Photosensitive resin printing plate original, process for producing the same and process for producing resin relief printing plate therewith

ABSTRACT

A photosensitive resin printing plate precursor including: a photosensitive resin layer (A) containing a water-soluble or water-dispersible resin and an ultraviolet-curable monomer; and a water-insoluble heat-sensitive mask layer (C) containing an infrared-absorbing material, deposited in that order on a support is disclosed. By introducing a crosslinked structure or a hydrophobic constituent to the heat-sensitive mask layer (C) so as to be insoluble in water, a difference in polarity is produced between the layers (A) and (C) and, thus, mass transfer between the two layers can be prevented. Also, the scratch resistance of the heat-sensitive mask layer (C) can be dramatically enhanced and, thus, the printing plate precursor becomes easy to handle.

TECHNICAL FIELD

The present invention relates to a photosensitive resin printing plateprecursor suitable for digital information transfer, which is to beexposed to light in an image form and then developed with water or awater-based liquid, to a method for producing the same, and to a methodfor producing a letterpress printing plate using the same.

BACKGROUND ART

Photosensitive resin compositions are generally used for printingplates, and their use is the mainstream in the fields of letterpressprinting, lithography, intaglio printing, and flexographic printing.

For such a printing plate, a photosensitive resin layer is brought intoclose contact with an original pattern film and exposed to light throughthe original pattern film so as to form portions soluble and insolublein a solvent, and thus a relief pattern is formed and used as a printingplate.

The printing plate requires a negative or a positive original patternfilm, and accordingly the time and cost of its production increase. Inaddition, since the original pattern film must be developed by chemicaltreatment and the waste liquid from the development must be treated, theuse of the printing plate involves environmental health problems.

A so-called CTP (computer to plate) process in which informationprocessed on a computer is directly output on a printing plate toprepare a relief printing plate without the step of forming an originalpattern film has been proposed in association with the advance ofcomputers. In the CTP process, an image mask is formed over aphotosensitive resin layer “in situ” with a laser controlled by digitaldata, and then, the entire surface of the photosensitive resin layer isexposed to active light, typically, ultraviolet light, through the imagemask, so that only the regions of photosensitive resin layer not coveredwith the image mask are selectively cured. The process has someadvantages. For example, since this process does not require theabove-described step of forming an original pattern film or treatment ofwaste liquid from development of the original pattern film, it isadvantageous in environmental health. In addition, the process canprovide a sharp relief.

Specifically, a method of forming an image mask coating on aphotosensitive recording component with an ink jet printer or anelectrophotographic printer has been proposed (see, for example, GermanPatent Publication No. 4117127 (Page 1)). Unfortunately, this methodcannot provide fine images.

Another method has also been proposed in which a photosensitiveflexographic recording material including a photosensitive elastomericlayer, an infrared-sensitive layer opaque to ultraviolet light, and acover sheet is irradiated with infrared laser light to form an imagemask coating (see, for example, U.S. Pat. No. 5,607,814 (columns 17 to18)). The upper portions of regions irradiated with infrared light ofthe infrared-sensitive layer adhere to the cover sheet. The regionsirradiated with infrared laser light of the infrared-sensitive layer areselectively removed by peeling off the cover sheet. Unfortunately, thismethod may give damage like scratches to the cover sheet, which candoubles as a protective layer, and thus the damage results in incompleteinformation transfer disadvantageously. Also, the development by peelingoff the infrared-sensitive layer causes the regions unirradiated withinfrared laser light to peel easily, and it is therefore unsuitable forthe formation of fine image masks.

Even in the field of relief printing, the CTP process has been generallyproposed for flexographic printing plate, which are made of anelastomeric binder, such as butadiene rubber or styrene rubber, as aresin, and can use an aqueous ink. On the other hand, in the field ofletterpress printing plate, which are made of a soluble resin instead ofthe elastomeric binder and can use an oil-based ink, there are fewmethods for the CTP process proposed. This is because the polarities ofthe infrared-sensitive layer and the photosensitive resin layer, whichis made of the soluble resin, are liable to be close, and consequentlythe infrared-sensitive layer and the photosensitive resin layer areliable to be mixed with time.

In the printing using flexographic plates, the printing between theplate cylinder and the impression cylinder is set weak because therelief to which an image is transferred is soft. The flexographic plateis suitable for printing on corrugated boards having uneven surfaces andflexible packaging films less resistant to high printing pressure. Incontrast, in the letterpress printing, the printing pressure between theplate cylinder and the impression cylinder can be set high. This isbecause the relief is so hard as not to be deformed by high printingpressure and, accordingly, the degradation of printing quality, such asincrease in width of letters, is prevented. By increasing printingpressure with use of a letterpress plate, ink can be applied at a largethickness to give a texture of strength to printed material, and metal,to which it is relatively difficult to transfer ink, can be printed on.

For the photosensitive letterpress printing plate using the CTP process,a photosensitive letterpress recording material has been proposed whichincludes a photosensitive resin layer, an oxygen-transmissive interlayerif necessary, an infrared-sensitive layer opaque to ultraviolet light,and a protective layer (see, for example, U.S. Pat. No. 6,020,108(columns 11 to 12)). After the protective layer is peeled off, theinfrared-sensitive layer is irradiated with infrared laser light to forman image mask. After the entire surface is exposed to ultraviolet light,the image mask and the uncured regions of the photosensitive layer areremoved by the same developer. The oxygen-transmissive interlayerprevents mass transfer between the photosensitive resin layer and theinfrared-sensitive layer and removal of the photosensitive resin layerby laser engraving. The infrared-sensitive layer is formed by adding aninfrared-absorbing and UV-blocking substance, such as carbon black, to awater-soluble or water-dispersible binder. The infrared-sensitive layer,however, does not have crosslinked structures, and is, accordingly,brittle against external flaws. It is therefore necessary to payattention to handling the material after peeling off the protectivelayer.

Another method has also been proposed in which the image mask is formedby irradiating with infrared laser light a photosensitive letterpressprinting plate precursor including a photosensitive resin layer, a filmlayer, and an infrared-sensitive layer on a substrate (see, for example,EP Patent Application Publication No. 1152296 (column 26)). In thismethod, the entire surface of the printing plate precursor is exposed toultraviolet light through the resulting image mask, and then the imagemask is peeled off and removed together with the film layer, followed bywater development to obtain a letterpress printing plate. This methoddoes not allow the constituents of the infrared-sensitive layer of theimage mask to contaminate the developer and the waste developer is easyto treat, advantageously. However, if the film layer between thephotosensitive resin layer and the infrared-sensitive layer has a largethickness, the large thickness easily causes ultraviolet light to curveor disperse. Consequently, if a less directional ultraviolet lightsource is used, the resulting image may become large undesirably.

In view of the above-described disadvantages, the object of the presentinvention is to provide a photosensitive resin printing plate precursorcapable of forming a protruding relief pattern without using anyoriginal pattern film, a method for producing the same, and a method forproducing a letterpress printing plate using the same.

DISCLOSURE OF INVENTION

In order to overcome the disadvantages, the present invention provides aphotosensitive resin printing plate precursor having the followingstructure:

the “photosensitive resin printing plate precursor comprising, on asupport in this order, a photosensitive resin layer (A) containing awater-soluble or water-dispersible resin and an ultraviolet-curablemonomer; a

water-insoluble heat-sensitive mask layer (C) containing aninfrared-absorbing material”.

In addition, a method for producing a photosensitive resin printingplate precursor is provided which is as follows:

the “method for producing a photosensitive resin printing plateprecursor, the method comprising the steps of:

-   (i) forming a photosensitive resin sheet by depositing a    photosensitive resin layer (A) on a substrate;-   (ii) forming a heat-sensitive mask element including a    water-insoluble heat-sensitive mask layer (C); and-   (iii) laminating the surface of the photosensitive resin layer (A)    of the photosensitive resin sheet to the heat-sensitive mask    element.”

Furthermore, a method for producing a letterpress printing plate isprovided which is as follows:

the “method for producing a letterpress printing plate, the methodcomprising the steps of:

-   (1) preparing the photosensitive resin printing plate precursor of    the present invention;-   (2) forming an image mask (C′) by imagewise irradiating the    heat-sensitive mask layer (C) with infrared laser;-   (3) exposing through the image mask (C′) to ultraviolet light to    form a latent image on the photosensitive resin layer (A); and-   (4) removing the image mask (C′) and portions unexposed to    ultraviolet light of the photosensitive resin layer (A) by    development with a water-based liquid.”

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention easily provides a photosensitive resin printingplate precursor capable of forming a protruding relief pattern withoutusing any original pattern film. The invention can be applied not onlyto letterpress printing plates which have protruding reliefs, but alsoto flexographic printing plates, intaglio printing plates, lithographicprinting plates, and stencil printing plates without limiting theapplications to these, as long as a photosensitive resin is used.

Embodiments of the present invention will now be described.

The photosensitive resin printing plate precursor of the presentinvention has a layered structure formed by depositing on a support inthis order, a photosensitive resin layer (A) and a heat-sensitive masklayer (C).

The photosensitive resin layer (A) of the present invention must containa water-soluble or water-dispersible resin and an ultraviolet-curablemonomer. The layer (A) is cured by exposing to ultraviolet light,preferably having a wavelength of 300 to 400 nm. The photosensitiveresin layer (A) is formed of a photosensitive resin composition in,preferably, a sheet with a thickness of 0.1 to 10 mm.

The above-mentioned photosensitive resin composition contains awater-soluble or water-dispersible resin and an ultraviolet-curablemonomer, and preferably further contains a photopolymerizationinitiator.

The water-soluble or water-dispersible resin of the present inventionfunctions as a carrier resin for retaining the form of thephotosensitive resin composition which turns out a solid state, andallows the photosensitive resin layer (A) to be developed in water. Suchresins include, for example, polyvinyl alcohol, polyvinyl acetate,partially saponified polyvinyl acetate (partially saponified polyvinylalcohol), cellulose resins, acrylic resins, polyamide resins having ahydrophilic group such as polyethylene oxide, ethylene/vinyl acetatecopolymers, and their modified forms. Among these, preferred arepolyvinyl alcohol, partially saponified polyvinyl alcohol, polyamideresins having a hydrophilic group, and their modified forms.

The ultraviolet-curable monomer can generally be crosslinked by radicalpolymerization, and is not particularly limited as long as it is capableof being crosslinked by radical polymerization. Examples of theultraviolet-curable monomer include compounds having a singleethylenically unsaturated bond, for example, (meth)acrylates having ahydroxy group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate, and β-hydroxy-β′-(meth)acryloyloxyethyl phthalate; alkyl(meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, isoamyl (meth)acrylate,2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl(meth)acrylate; cycloalkyl (meth)acrylates, such as cyclohexyl(meth)acrylate; haloalkyl (meth)acrylates, such as chloroethyl(meth)acrylate and chloropropyl (meth)acrylate; alkoxyalkyl(meth)acrylate, such as methoxyethyl (meth)acrylate, ethoxyethyl(meth)acrylate, and butoxyethyl (meth)acrylate; phenoxyalkyl(meth)acrylates, such as phenoxyethyl acrylate and nonylphenoxyethyl(meth)acrylate; alkoxyalkylene glycol (meth)acrylates, such asethoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol(meth)acrylate, and methoxydipropylene glycol (meth)acrylate;(meth)acrylamides, such as (meth)acrylamide, diacetone (meth)acrylamide,and N,N′-methylene-bis-(meth)acrylamide; 2,2-dimethylaminoethyl(meth)acrylate; 2,2-diethylaminoethyl (meth)acrylate;N,N-dimethylaminoethyl (meth)acrylamide; and N,N-dimethylaminopropyl(meth)acrylamide. The ultraviolet-curable monomers also includecompounds having at least two ethylenically unsaturated bonds, forexample, polyethylene glycol di(meth)acrylates, such as diethyleneglycol di(meth)acrylate; polypropylene glycol di(meth)acrylates, such asdipropylene glycol di(meth)acrylate; trimethylolpropanetri(meth)acrylate; pentaerythritol tri(meth)acrylate; pentaerythritoltetra(meth)acrylate; glycerol tri(meth)acrylate; polyvalent(meth)acrylates prepared by adding a compound having an ethylenicallyunsaturated bond and an activated hydrogen, such as an unsaturatedcarboxylic acid or an unsaturated alcohol, to ethylene glycol diglycidylether; polyvalent (meth)acrylates prepared by addition reaction of anunsaturated epoxy compound, such as glycidyl (meth)acrylate, with acompound having an activated hydrogen, such as a carboxylic acid or anamine; polyvalent (meth)acrylamides, such asmethylene-bis-(meth)acrylamide; and polyvalent vinyl compounds, such asdivinyl benzene.

The photopolymerization initiator suitably used in the present inventionis not particularly limited, as long as it can polymerize polymerizableunsaturated carbon-carbon bonds with light. Among others preferred arecompounds capable of producing radicals by self-cleavage or hydrogenremoval, such as benzoin alkyl ethers, benzophenones, anthraquinones,benzils, acetophenones, and diacetyls.

In order to enhance the compatibility and flexibility, anotherconstituent, for example, a polyvalent alcohol may be added to thephotosensitive resin composition. Such polyvalent alcohols includeethylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, glycerin, trimethylol propane, and trimethylol ethane. A knownpolymerization inhibitor may also be added to enhance the thermalstability. Preferred polymerization inhibitors include phenols,hydroquinones, and catechols. Other additives may also be added, such asdye, pigment, surfactant, UV absorber, perfume, and antioxidant.

The process for producing the photosensitive resin layer (A) from thephotosensitive resin composition is not particularly limited. Forexample, after a carrier resin is dissolved in a solvent, a UV-curablemonomer and a photopolymerization initiator are added to the solutionand the mixture is sufficiently stirred to yield a solution of thephotosensitive resin composition. The resulting solution is subjected toremoval of the solvent, and then melt-extruded onto a support which is,preferably, coated with an adhesive. Alternatively, the solution inwhich part of the solvent remains may be melt-extruded onto a supportcoated with an adhesive, and then the remaining solvent is air-driedwith time to yield the photosensitive resin layer (A).

The material of the support used in the present invention is notparticularly limited, but preferably has dimensional stability. Suchsupport materials include, for example, metal plates, such as of steel,stainless steel, and aluminium; plastic sheets, such as of polyester;and synthetic rubber sheets, such as of styrene-butadiene rubber.

The heat-sensitive mask layer (C) used in the present invention has thefollowing functions: (1) the mask layer efficiently absorbs infraredlaser light to generate heat, so that the heat momentarily causes a partor the entirety of the mask layer to evaporate or ablate, therebyproviding a difference in optical density between laser irradiated andno-irradiated areas, that is, reducing the optical density in theirradiated areas; (2) the mask layer essentially blocks ultravioletlight.

The heat-sensitive mask layer (C) is a water-insoluble heat-sensitivelayer containing an infrared-absorbing material. Preferably, the layer(C) further contains a pyrolyzable compound capable of being evaporatedor ablated by heat and a UV-absorbing material having a function toblock ultraviolet light, in addition to the infrared-absorbing material,which absorbs infrared laser light to convert the light into heat.

Having a function to block ultraviolet light herein means that theoptical density of the heat-sensitive mask layer (C) is 2.5 or more,preferably 3.0 or more. In general, optical density is represented by Dand defined by the following equation:D=log₁₀(100/T)=log₁₀(I ₀ /I)(where T represents transmittance (unit: %); I₀ represents intensity ofincident light for measuring transmittance; and I represents transmittedlight intensity).

The optical density may be derived from a measured transmitted lightintensity with the incident light intensity set constant, or derivedfrom a measured incident light intensity required to reach a transmittedlight intensity. In the present invention, the optical density refers toa value derived from the former, that is, transmitted light intensity.

The optical density can be measured by use of an orthochromatic filterand a Macbeth transmission densitometer TR-927 (manufactured byKollmorgen Instruments Corp.).

The infrared-absorbing material is not particularly limited, as long asit can absorb infrared light and convert the light into heat. Examplesof the infrared-absorbing material include: black pigments, such ascarbon black, aniline black, and cyanine black; green pigments, such asphthalocyanines and naphthalocyanine; rhodamine dyes; naphthoquinonedyes; polymethine dyes; diimonium salts; azoimonium dyes; chalcogendyes; carbon graphite; iron powder; diamine metal complexes; dithiolmetal complexes; phenolthiol metal complexes; mercaptophenol metalcomplexes; arylaluminium metal salts; crystal water-containing inorganiccompounds; copper sulfate; chromium sulfide; silicates; metal oxides,such as titanium oxide, vanadium oxide, manganese oxide, iron oxide,cobalt oxide, and tungsten oxide; hydroxides and sulfates of thesemetals; and metal powders, such as those of bismuth, tin, tellurium,iron, and aluminium.

Among these preferred is carbon black, from the viewpoint ofphotothermal conversion efficiency, cost efficiency, and ease ofhandling, and further ultraviolet absorption described later. Carbonblack is classified into furnace black, channel black, thermal black,acetylene black, lampblack, and others, according to the manufacturingprocess. Among these, furnace black is preferably used because it hascommercially available various types in, for example, grain size and iscommercially inexpensive.

The infrared-absorbing material is used preferably in an amount of 2 to75 percent by weight, more preferably 5 to 70 percent by weight,relative to the entire weight of the heat-sensitive mask layer (C). Anamount of 2 percent by weight or more leads to efficient photothermalconversion, and an amount of 75 percent by weight or less prevents thelack of other constituents which is likely to cause the heat-sensitivemask layer (C) to be scratched.

Examples of the pyrolyzable compound used in the layer (C) includeammonium nitrate, potassium nitrate, sodium nitrate, nitro compoundssuch as nitrocellulose, organic peroxides, polyvinyl pyrrolidone, azocompounds, diazo compounds, hydrazine derivatives, and the metals andmetal oxides listed in the section of the infrared-absorbing material.Preferably, macromolecular compounds are used, such as polyvinylpyrrolidone and nitrocellulose, from the viewpoint of, for example, easyapplication of solution.

In the use of nitrocellulose, the viscosity of nitrocellulose ispreferably 1/16 to 1 second and more preferably ⅛ to ½ second when theviscosity is measured in accordance with the method specified in ASTMD301-72. The viscosity corresponds to the polymerization degree ofnitrocellulose, and a low viscosity refers to a low polymerizationdegree. If the viscosity is 1/16 seconds or more, the polymerizationdegree of nitrocellulose becomes so high as to prevent scratches in thesurface of the heat-sensitive mask layer (C); if the viscosity is 1second or less, inconvenience in handling resulting from high viscosityis prevented.

Nitrocellulose is liable to generate harmful NOx gas when it ispyrolyzed. If the heat-sensitive mask layer (C) contains nitrocellulose,it is necessary that the plate setter for drawing a mask pattern with aninfrared laser is directly equipped with an air-collecting unit fordrawing generated NOx and a unit for decomposing the NOx into harmlesscompounds. Accordingly, the plate setter comes to a large size andbecomes expensive, disadvantageously.

This disadvantage can be solved by use of a pyrolyzable compoundcontaining no NOx source, such as the nitro group.

Acrylic resin is relatively easy to pyrolyze and provide no fear ofgenerating NOx because it contains no nitrogen atom. Acrylic resin istherefore preferably used as an alternative pyrolyzable compound tonitrocellulose. In general, acrylic resin has a pyrolysis temperature of190 to 250° C. If the prevention of NOx generation is primarilyintended, it is preferable that the heat-sensitive mask layer (C) do notsubstantially contain nitrocellulose. Not substantially containingnitrocellulose means that the nitrocellulose content in the compositionof the heat-sensitive mask layer (C) is 2 percent by weight or less.This is because a nitrocellulose content of 2 percent by weight or lessreduces the amount of NOx generated to such a level as does not causeenvironmental health problems.

Acrylic resin is a polymer or copolymer of at least one monomer selectedfrom the group consisting of acrylic acids, methacrylic acids,acrylates, and methacrylates.

Since mass transfer to the underlying photosensitive resin layer (A) canbe prevented by use of an acrylic resin insoluble in water and alcohol,water/alcohol-insoluble acrylic resins are more preferably used.

The pyrolyzable compound is used in an amount of, preferably, 80 percentby weight or less, more preferably 15 to 60 percent by weight, relativeto the entire composition of the heat-sensitive mask layer (C). Use of80 percent by weight or less of pyrolyzable compound prevents theoccurrence of difficulty in pyrolyzing the pyrolyzable compound,resulting from the decrease in amount of a photothermal conversionmaterial described below.

The UV-absorbing material suitably used in the layer (C) is notparticularly limited, but is preferably a compound having an absorptionband in the region of 300 to 400 nm. Examples of such compounds includebenzotriazole compounds, triazines, benzophenone compounds, carbonblack, and the metals and metal oxides listed in the section of theinfrared-absorbing material. Among these preferred is carbon blackbecause it exhibits absorption in the region of infrared as well as inthe region of ultraviolet and functions as a photothermal conversionmaterial.

The UV-absorbing material is used preferably in an amount of 0.1 to 75percent by weight, more preferably 1 to 50 percent by weight, relativeto the entire composition of the heat-sensitive mask layer (C). Use ofat least 0.1 percent by weight of UV-absorbing material provides anoptical density required, and use of 75 percent by weight or less ofUV-absorbing material prevents lack of other constituents, which islikely to cause the heat-sensitive mask layer (C) to be scratched.

The heat-sensitive mask layer (C) is deposited on the photosensitiveresin layer (A) directly or with an adhesion-adjusting layer (B) theirbetween. The photosensitive resin layer (A) is constituted of aso-called hydrophilic composition containing a water-soluble orwater-dispersible resin. If the adhesion-adjusting layer (B), which willbe described later, is also constituted of a so-called hydrophiliccomposition containing a water-soluble or water-dispersible resin, aheat-sensitive mask layer (C) constituted of a hydrophilic compositioncauses mass transfer between the layers to degrade the intrinsicfunction of each layer. For example, if an monomer of the photosensitiveresin layer (A) transfers into the heat-sensitive mask layer (C), thelaser ablation characteristics of the heat-sensitive mask layer (C) aredegraded; if the photosensitive resin layer (A) is contaminated with theUV-absorbing material, the photosensitive resin layer cannot be cured byultraviolet light.

The heat-sensitive mask layer (C) used in the present invention,therefore, needs to have hydrophobicity. Hydrophobicity herein refers toinsolubility in water, that is, the heat-sensitive mask layer (C) hascharacteristics not allowing development in water independently. In caseof using metals or metal oxides as the heat-sensitive layer, these areintrinsically hydrophobic. But in case of using organic materials, suchas carbon black, it is necessary to take measures. The approach forgiving water insolubility is not particularly limited. For example, theentire composition of heat-sensitive mask layer (C) may be composed ofhydrophobic constituents, or the layer may be crosslinked by using acurable resin as a binder. The latter approach is preferable because, inthis approach, by increasing the molecular weight of constituents in theheat-sensitive mask layer (C), the mass transfer between the layers canbe made more difficult. This approach also produces the effect of givingscratch resistance to the surface of the heat-sensitive mask layer (C),advantageously. Specifically, the scratch resistance is preferably suchthat no scratch penetrates through the heat-sensitive mask layer (C)even by five reciprocations, more preferably ten reciprocations, ofrubbing the surface of the heat-sensitive mask layer (C), with a whitecotton cloth wetted with water to which a load of 500 g (the weight ofthe frictionizer: 200 g; additional weight: 300 g) is applied with acolor fastness rubbing tester II specified in JIS L 0823.

In the use of a curable resin as a binder, the method for curing theresin is not particularly limited, but curing by light is difficult orinefficient because the heat-sensitive mask layer (C) absorbsultraviolet light. So curing by heat is preferable. Thermosetting resinsacting as the binder include, for example, combinations of at least onecompound selected from the group consisting of multifunctionalisocyanates and multifunctional epoxy compounds and at least onecompound selected from the group consisting of urea-based resins,amine-based compounds, amide-based compounds, hydroxy group-containingcompounds, carboxylic compounds, and thiol-based compounds.

Multifunctional isocyanates need to be cured at high temperature becauseit is difficult to complete the reaction in a short time. However, ifnitrocellulose is used as the pyrolyzable compound, it is not permittedto be cured at 180° C. or more because it pyrolyze at 180° C. Forcrosslinking, therefore, a combination is preferably applied which isconstituted of a multifunctional epoxy compound and at least onecompound selected from the group consisting of urea-based resins,amine-based compounds, amide-based compounds, hydroxy group-containingcompounds, carboxylic compounds, and thiol-based compounds.

The multifunctional epoxy compounds include, for example, bisphenolA-type epoxy resins, bisphenol F-type epoxy resins, and glycidylether-type epoxy resins.

The urea-based resins include butylated urea resins, butylated melamineresins, butylated benzoguanamine resins, butylated urea-melaminecocondensed resins, aminoalkyd resins, iso-butylated melamine resins,methylated meminine resins, hexamethoxymethylolmelamine, methylatedbenzoguanamine resins, and butylated benzoguanamine resins.

The amine-based compounds include diethylenetriamine,triethylenetriamine, tetraethylenepentamine, diethylaminopropylamine,N-aminoethylpiperazine, meta-xylenediamine, meta-phenylenediamine,diaminodiphenylmethane, diaminodiphenylsulfone, and isophorone diamine.

The amide-based compounds include polyamide-based curing agents used forcuring epoxy resins and dicyandiamide. The hydroxy group-containingcompounds include phenol resins and polyvalent alcohols. The thiol-basedcompounds include polyvalent thiols.

Preferred carboxylic acids include phthalic acid, hexahydrophthalicacid, tetrahydrophthalic acid, dodecynylsuccinic acid, pyromelliticacid, chloren acid, maleic acid, fumaric acid, and their anhydrides.

A curable resin of a single constituent may be used as alternative tothe curable resin of plural constituents. Such curable resins of asingle constituent include epoxy resins, melamine resins, urethaneresins, crosslinkable polyester resins, and crosslinkable polyamideresins. These resins may be used in combination.

The thermosetting resin is used in an amount of preferably 10 to 75percent by weight, more preferably 30 to 60 percent by weight, relativeto the entire composition of the heat-sensitive mask layer (C). Tenpercent by weight or more of thermosetting resin provides a crosslinkedstructure sufficient to ensure water-insolubility, and 75 percent byweight or less of the thermosetting resin efficiently allows laserablation of the heat-sensitive mask layer (C).

If a pigment, such as carbon black, is used as the infrared-absorbingmaterial, a plasticizer, a surfactant, or a dispersant may be added sothat the pigment is easy to disperse.

The method for forming the heat-sensitive mask layer (C) is notparticularly limited. For example, vapor deposition or sputtering may beadopted in use of a metal oxide; a composition of the heat-sensitivemask layer, which may be used as it is or be dissolved in a solvent, maybe applied by coating and subsequently cured by heat, in use of anorganic material, such as carbon black.

The heat-sensitive mask layer (C) formed by coating has a thickness ofpreferably 0.5 to 10 μm, more preferably 1 to 3 μm. A thickness of 0.5μm or more can make it difficult to scratch the surface of the layer,prevent leakage of light, and provide a certain level of opticaldensity. Furthermore, the formation of such a thickness does not requireany advanced application technique. A thickness of 10 μm or less doesnot require high energy for ablating the heat-sensitive mask layer (C),and is thus advantageous in costs.

The heat-sensitive mask layer (C) formed by vapor deposition orsputtering of a metal or a metal oxide is preferably thin, as long ashigh optical density is ensured. The thickness of a thin layer affectsthe sensitivity. Specifically, an excessively large thickness requiresadditional energy for vaporizing or melting the thin layer, andaccordingly the ablation sensitivity of the heat-sensitive mask layer(C) is degraded. Thus, the thickness of the thin layer is preferably 100nm or less, more preferably 2 to 100 nm, and particularly preferably 4to 20 nm. Even a thickness of less than 2 nm may reduce the sensitivity.

Preferably, vacuum vapor deposition, which is one type of vapordeposition, is adopted. Specifically, a metal and carbon are heated tovaporize in a container of a reduced pressure of 10⁻⁴ to 10⁻⁷ mmHg, anddeposited into a thin film on a substrate.

For sputtering, a direct or alternating voltage is applied to a pair ofelectrodes to cause glow discharge in a container of a reduced pressureof, for example, 10⁻¹ to 10⁻³ mmHg, and thus a thin film is formed on asubstrate by a sputtering phenomenon at the cathode, or at the groundingelectrode in the case where an alternating voltage is applied.

Such a thin film having a high optical density required in the presentinvention is typically a carbon thin film. The carbon thin film hereinis amorphous, different from so-called diamond thin films or graphitethin films. The amorphous carbon thin film can be selectively producedby general vacuum-vapor deposition, such as ion beam vapor depositionand ionized vapor deposition; or sputtering, such as ion beamsputtering.

The carbon thin film is preferably formed by either vacuum vapordeposition or sputtering.

In vacuum vapor deposition for forming the carbon thin film, preferably,carbon is heated to vaporize in a container of a reduced pressure of,for example, 10⁻⁴ to 10⁻⁷ mmHg, and deposited on the surface of asubstrate. It is preferable that carbon be heated at an appropriatetemperature and deposited taking a long time, because the melting pointof carbon is as high as 3923 K.

In sputtering for forming the carbon thin film, preferably, a direct oralternating voltage is applied to a pair of electrodes to cause glowdischarge in a container of a reduced pressure of, for example, 10⁻¹ to10⁻³ mmHg, and thus the thin film is formed on a substrate by asputtering phenomenon at the cathode. By this method, even carbon, whichhas a high melting point, can be relatively easily formed into a thinfilm.

In addition to the carbon thin film, metal thin films can serve as theheat-sensitive mask layer (C). Exemplary metal thin films are made of,but not limited to, tellurium, tin, antimony, gallium, magnesium,polonium, selenium, thallium, zinc, aluminum, silicon, germanium, tin,copper, iron, molybdenum, nichrome, indium, iridium, manganese, lead,phosphorus, bismuth, nickel, titanium, cobalt, rhodium, osnium, mercury,barium, palladium, bismuth, and compounds listed in Japanese ExaminedPatent Application Publication No. 41-14510, such as silicon carbide,boron nitride, boron phosphide, aluminium phosphide, alloys of antimonyand aluminum, alloys of gallium and phosphorus, and alloys of galliumand antimony. Among these preferred are tellurium, tin, antimony,gallium, magnesium, polonium, selenium, thallium, zinc, bismuth, andaluminium.

It is preferable that the metal used for the layer (C) be less lustrous,from the viewpoint of sensitivity, because highly lustrous metalsreflect laser light large at the surface.

Any metal may be used in the layer (C), as long as the metal can bepartially or entirely vaporized or melted instantaneously and has amelting point of 2000 K or less. It takes a long time to vaporize ormelt a metal having a melting point of more than 2000 K even by laserexposure, and consequently the ablation sensitivity of the layer (C) isdegraded. More preferably, the melting point is 1000 K or less.Specifically, such metals include preferably tellurium, tin, antimony,gallium, magnesium, polonium, selenium, thallium, zinc, bismuth, andaluminum, more preferably tellurium (melting point: 449.8° C.), tin(melting point: 232° C.), zinc (melting point: 419.5° C.), and aluminum(melting point: 660.4° C.). These metals are particularly preferablebecause thin films made of these metals are easily vaporized or meltedby heat of laser exposure.

Since alloys of two or three metals selected from the above-listedmetals have low melting points and are sensitive, such alloys areparticularly suitable for the layer (C). Specifically, such alloys areconstituted of preferably tellurium and tin; tellurium and antimony;tellurium and gallium; tellurium and bismuth; and tellurium and zinc,more preferably tellurium and zinc; and tellurium and tin. Alloys ofthree constituents include preferably those of tellurium, tin, and zinc;tellurium, gallium, and zinc; tin, antimony, and zinc; and tin, bismuth,and zinc, more preferably tellurium, tin, and zinc; and tin, bismuth,and zinc.

The metal thin film may be formed by any process, but preferably byvacuum vapor deposition or sputtering.

A thin film containing carbon and a metal may also be used as theheat-sensitive mask layer (C). By simultaneous vapor deposition orsputtering of carbon and a metal, the optical density of the thin filmis increased, so that the thin film more easily absorbs infrared laserlight advantageously. In this instance, various types of metal may beused. The metal or alloy used in this case is not particularly limited,as long as it allows vapor deposition or sputtering. Preferably, themetal has a melting point of 2000 K or less, and more preferably 1000 Kor less. A metal having a melting point of more than 2000 K does noteasily form images even by simultaneous vapor deposition or sputteringof carbon and the metal.

In the simultaneous vapor deposition or sputtering of carbon and themetal, the carbon content in the resulting thin film is preferably 10percent by weight or more, and more preferably 30 percent by weight ormore. A carbon content of less than 10 percent by weight reduces theabsorption of infrared laser light, and consequently the sensitivity islikely to deteriorate.

An adhesion-adjusting layer (B) may be provided between thephotosensitive resin layer (A) and the heat-sensitive mask layer (C).The adhesion-adjusting layer (B) enhances the adhesion between the layer(A) and the layer (C) when the adhesion between the layer (A) and thelayer (C) is weak, and reduces the adhesion between the layer (A) andthe layer (C) when the adhesion between these layers is so strong as tonegatively affect the laser ablation characteristics of the layer (C).In addition, the adhesion-adjusting layer (B) certainly prevents masstransfer between the layer (A) and the layer (C), and laser ablation ofthe photosensitive resin layer (A).

If adhesion between the layer (A) and the layer (C) is excessivelystrong, either or both of the layers may be cohesive or contain afunctional group contributing to the adhesion. In such cases, theadhesion-adjusting layer (B) can be provided to reduce the adhesionbetween the layers. Against highly cohesive layers (A) and (C), a resinused for preventing cohesiveness, such as polyvinyl alcohol orcellulose, can be used to accomplish the purpose. Against the layerscontaining a functional group contributing to the adhesion, a resin lessinteracting with the functional group can be used.

If the adhesion-adjusting layer (B) is provided in order to enhance theadhesion between the layer (A) and the layer (C), the layer (B) ispreferably formed of a compound having both a hydrophilic group and ahydrophobic group because the photosensitive resin layer (A) ishydrophilic and the heat-sensitive mask layer (C) is hydrophobic.Examples of such a compound include a resin prepared by introducing ahydroxy group to the water-insoluble resin used in the heat-sensitivemask layer (C); and an uncured form of the thermosetting resin used inthe heat-sensitive mask layer (C).

The adhesion-adjusting layer (B) may be constituted of a water-solubleor water-dispersible resin from the viewpoint of water development, andpreferably the water-soluble or water-dispersible resins listed in thesection of the photosensitive resin layer (A) are suitably used.Specifically, preferred are polyvinyl alcohol, polyvinyl acetate,partially saponified polyvinyl acetate (partially saponified polyvinylalcohol), cellulose resins, acrylic resins, polyamide resins having ahydrophilic group, such as polyethylene oxide, and ethylene/vinylacetate copolymers. An additive, such as a surfactant, may be added tothese resins. After depositing the adhesion-adjusting layer (B), theconstituent of the adhesion-adjusting layer may be diffused into thephotosensitive resin layer (A) to assimilate into the layer (A).

The thickness of the adhesion-adjusting layer (B) is preferably 15 μm orless, and more preferably 0.3 to 5 μm. A thickness of 15 μm or less canprevent ultraviolet exposure light from curving or diffusing at theadhesion-adjusting layer, thus allowing the formation of sharp reliefpatterns. An adhesion-adjusting layer (B) having a thickness of 0.3 μmor more is easy to form.

A protective layer (E) may be provided over the heat-sensitive masklayer (C). The layer (E) is used to protect the heat-sensitive masklayer (C) against external flaws. Preferably, the protective layer (E)may be made of a polymer film capable of being peeled off from theheat-sensitive mask layer (C). Examples of the protective layer (E)include films of polyester, polycarbonate, polyamide, fluoropolymer,polystyrene, polyethylene, and polypropylene. Alternatively, the layer(E) may be a release paper coated with silicone.

The thickness of the protective layer (E) is preferably 25 to 200 μm,and more preferably 50 to 150 μm. A thickness of 25 μm or more leads toeasy handling and can protect the heat-sensitive mask layer (C) againstexternal flaws; a thickness of 200 μm or less reduces the cost and leadsto economical advantage, and the layer having such a thickness is easyto peel off.

The heat-sensitive mask layer (C) may be covered with a peel assistlayer (D). Preferably, the layer (D) is disposed between the layer (C)and the layer (E). Preferably, the peel assist layer (D) makes it easyto peel off itself alone, only the protective layer (E), or both theprotective layer (E) and the separation aid layer (D) from thephotosensitive resin printing plate precursor. If the protective layer(E) is directly disposed on the heat-sensitive mask layer (C) withstrong adhesion between these layers, the protective layer (E) may bedifficult to peel off or be easily peeled off together with theheat-sensitive mask layer (C).

Preferably, the peel assist layer (D) is made of a material adhesive tothe heat-sensitive mask layer (C) and less adhesive to the protectivelayer (E) to the extent that the protective layer (E) can be peeled off,or a material less adhesive to the heat-sensitive mask layer (C) to theextent that it can be peeled off from the heat-sensitive mask layer (C)and adhesive to the protective layer (E). The peel assist layer (D) mayremain as the outermost layer on the heat-sensitive mask layer sideafter the peeling off of the protective layer (E). It is thereforepreferable that the peel assist layer (D) is not cohesive from theviewpoint of handling, and is substantially transparent becauseultraviolet exposure light runs through this layer.

Exemplary constituents of the peel assist layer (D) include polyvinylalcohols, polyvinyl acetates, partially saponified polyvinyl alcohols,hydroxyalkyl celluloses, alkyl celluloses, and polyamide resins.Preferably, resins are used which mainly contain less cohesiveconstituents capable of being dissolved or dispersed in water. Amongthese, preferred are partially saponified polyvinyl alcohols having adegree of saponification of 60 to 99 mol %; and hydroxyalkyl cellulosesand alkyl celluloses having an alkyl group with a carbon number in therange of 1 to 5, from the viewpoint of cohesiveness.

The layer (D) may further contain an infrared-absorbing material and/ora pyrolyzable material so as to be easily ablated. The above-listedinfrared-absorbing material and pyrolyzable material materials can beused. The layer (D) may also contain a surfactant in order to enhancethe coating characteristics and wettability.

The thickness of the peel assist layer (D) is preferably 6 μm or less,and more preferably 0.1 to 3 μm. A thickness of 6 μm or less does notnegatively affect the laser ablation characteristics of the underlyingheat-sensitive mask layer (C). The layer (D) having a thickness of 0.1μm or more is easy to form.

If the protective layer (E) is peeled off from the photosensitive resinprinting plate precursor at a speed of 200 mm/min, the peel strength percentimeter is preferably 0.5 to 20 g/cm, and more preferably 1 to 15g/cm. A peel strength of 0.5 g/cm or more allows work withoutundesirable undesirable peeling of the protective layer (E), and a peelstrength of 20 g/cm or less allows the protective layer (E) to be easilypeeled off.

Preferred embodiments of the method for producing the photosensitiveresin printing plate precursor of the present invention will now bedescribed.

A first embodiment produces a printing plate precursor including thephotosensitive resin layer (A), optionally the adhesion-adjusting layer(B), the heat-sensitive mask layer (C), the peel assist layer (D), andthe protective layer (E) which are deposited in that order on asubstrate. This precursor is produced by laminating a heat-sensitivemask sheet to a photosensitive resin sheet. The heat-sensitive masksheet includes the layer (D), the layer (C), and optionally the layer(B) deposited by coating in that order on the protective layer (E). Thephotosensitive resin sheet includes the layer (A) deposited on thesubstrate. The lamination process is not particularly limited. Forexample, the heat-sensitive mask sheet may be laminated to the surfaceof the layer (A) or layer (B) swelled with water and/or alcohol; thephotosensitive resin sheet and the heat-sensitive mask sheet may belaminated with a viscous liquid having a composition that is the same asor similar to the layer (A), injected between the two sheets; or the twosheets may be pressed with a pressing machine at room temperature orwhile being heated.

A second embodiment produces a printing plate precursor including thephotosensitive resin layer (A), optionally the adhesion-adjusting layer(B), and the heat-sensitive mask layer (C) deposited in that order on asubstrate. First, if the layer (B) is provided, a solution containingthe constituent of the layer (B) is applied onto the surface of thephotosensitive resin sheet prepared by depositing the photosensitiveresin layer (A) on a substrate by the method described in the firstembodiment, followed by drying. Then, the resulting layer is coated witha liquid in which the constituent of the heat-sensitive mask layer (C)is dissolved or dispersed, and the liquid is heated to cure.

Alternatively, the layer (C) and optionally the layer (B) are depositedin that order on a release paper by the same coating to prepare aheat-sensitive mask sheet, then the photosensitive resin sheet includingthe layer (A) deposited on a substrate is laminated to theheat-sensitive mask sheet such that the layer (A) comes into contactwith the layer (B) or layer (C), and finally the release paper isremoved. The removed release paper can be advantageously reused for thesame purpose.

A third embodiment produced a printing plate precursor including thephotosensitive resin layer (A), optionally the adhesion-adjusting layer(B), the heat-sensitive mask layer (C), and the peel assist layer (D)deposited in that order on a substrate. This printing plate precursorcan be obtained by peeling off the protective layer (E) from theprinting plate precursor produced in the first embodiment. In thisinstance, the peeled protective layer (E) can be reused advantageously.

A fourth embodiment produces a printing plate precursor including thephotosensitive resin layer (A), optionally the adhesion-adjusting layer(B), the heat-sensitive mask layer (C), and the protective layer (E)deposited in that order on a substrate. This printing plate precursor isproduced by laminating a heat-sensitive mask sheet including the layer(C) and the layer (B) deposited by coating in that order on theprotective layer (E) to a photosensitive resin sheet including the layer(A) deposited on a substrate.

The photosensitive resin printing plate precursor prepared by theabove-descried method results in a letterpress printing plate throughthe following process.

The method for producing a letterpress printing plate of the presentinvention include the steps of: (1) preparing the above-describedphotosensitive resin printing plate precursor; (2) forming an image mask(C′) by imagewise irradiating the heat-sensitive mask layer (C) withinfrared laser; (3) exposing through the resulting image mask (C′) toultraviolet light to form a latent image on the photosensitive resinlayer (A); and (4) performing development with a water-based liquid toremove the image mask (C′) and the portions unexposed to ultravioletlight of the photosensitive resin layer (A) and subsequently removingthe developer by drying.

If the precursor includes the layer (E) or the layer (D) and layer (E),preferably, the image mask (C′) is formed by imagewise irradiating theheat-sensitive mask layer (C) with infrared laser light, after removalof at least the layer (E). More preferably, the heat-sensitive masklayer (C) is imagewise irradiated with infrared laser light to formimage mask (C′) after removing only the layer (E) from the precursorincluding the layer (D) and the layer (E).

In the step of (2) forming an image mask (C′) by imagewise irradiatingthe heat-sensitive mask layer (C) with infrared laser light, infraredlaser light is switched on/off according to image data, and isirradiated to the heat-sensitive mask layer (C) while scanning the masklayer. The heat-sensitive mask layer (C) irradiated with the infraredlaser light generates heat due to the action of the infrared-absorbingmaterial. The heat decomposes the pyrolyzable compound to remove theheat-sensitive mask layer (C). Thus, laser ablation is performed. Theoptical density in the region subjected to the laser ablation is largelyreduced, and the region becomes substantially transparent to ultravioletlight. By selectively performing laser ablation on the heat-sensitivemask layer (C) according to image data, the image mask (C′) is formedwhich can provide a latent image on the photosensitive resin layer (A).

For the irradiation of infrared laser, a laser having an oscillationwavelength in the range of 750 to 3000 nm is used. Examples of such alaser include solid lasers, such as ruby lasers, alexandrite lasers,perovskite lasers, Nd-YAG lasers, and emerald glass lasers;semiconductor lasers, such as InGaAsP, InGaAs, and GaAsAl lasers; anddye lasers, such as rhodamine lasers. A fiber laser amplifying theselight source may also be used. Among these preferred are semiconductorlasers because they have been downsized through the recent advances intechnology and are more economically advantageous than other lasersources. In addition, Nd-YAG lasers, which are often used for dental andmedical cares, are preferable because of their high power and economicaladvantage.

In the step of (3) exposing through the resulting image mask (C′) toultraviolet light to form a latent image on the photosensitive resinlayer (A), the entire surface of the photosensitive resin printing plateirradiated with laser light is exposed to ultraviolet light, preferablyhaving a wavelength of 300 to 400 nm, through the image mask (C′) inwhich an image pattern has been formed with the laser, and thus theportions of the photosensitive resin layer (A) underlying the regionssubjected to laser ablation of the image mask (C′) are selectivelycured.

Since ultraviolet light enters the photosensitive resin printing plateeven from the sides during exposure, it is preferable that a cover nottransmissive to ultraviolet light be provided over the side surfaces.Light sources achieving exposure to light having a wavelength of 300 to400 nm include high-pressure mercury lamps, super-high-pressure mercurylamps, metal halide lamps, xenon lamps, carbon arc lamps, and chemicallamps. The portions exposed to ultraviolet light of the photosensitiveresin layer (A) are turned insoluble or nondispersible in developer.

The step of (4) performing development with a water-based liquid toremove the image mask (C′) and the portions unexposed to ultravioletlight of the photosensitive resin layer (A) may be carried out, forexample, by developing the photosensitive resin layer (A) with a brushwasher or a spray washer using a water-based developer capable ofdissolving or dispersing the photosensitive resin layer (A).Consequently, the portions exposed to ultraviolet light are left toyield a letterpress printing plate having a relief pattern.

If the peel assist layer (D) remains, this layer is preferably removedin the step of (4), by development.

The water-based developer contains tap water, distilled water, or wateras the primary constituent, and optionally an alcohol having a carbonnumber of 1 to 6. The primary constituent means that its content is 70percent by weight or more. The water-based developer may further containthe constituents of the photosensitive resin layer (A), theadhesion-adjusting layer (B), the heat-sensitive mask layer (C), or thepeel assist layer (D).

The image mask (C′) is insoluble in water in order to enhance thescratch resistance, and is therefore insoluble in the developercontaining water and alcohol. However, the image mask (C′) can bephysically removed by scrubbing with an rigid brush, for example, a PBT(polybutylene terephthalate) brush because it is a thin film, which isadvantageous in the view of cost. In this case, by use of developingwater having a relatively high temperature of 30° C. to 70° C., theimage mask (C′) can be efficiently removed.

Then, additional treatment may be applied if necessary. For example, thedeveloper attached on the surface of the plate is dried, thephotosensitive resin printing plate is additionally exposed to light, orthe cohesiveness of the plate is eliminated.

The letterpress printing plate produced by the method of the presentinvention can be incorporated in a printing press and thus usedsuitably.

EXAMPLES

The present invention will be further described in detail with referenceto Examples.

<Synthesis of Water-Soluble Polyamide Resin 1>

Acrylonitrile was added to both ends of polyethylene glycol having anumber average molecular weight of 600, followed by hydrogen reductionto yield α, ω-diaminopolyoxyethylene. Melted and polymerized were 60parts by weight of an equimolar salt of the α, ω-diaminopolyoxyethyleneand adipic acid, 20 parts by weight of ε-caprolactam, and 20 parts byweight of an equimolar salt of hexamethylene diamine and adipic acid toyield water-soluble polyamide resin 1 having a relative viscosity(viscosity of 1 g of polymer dissolved in 100 mL of chloral hydrate,measured at 25° C.) of 2.50.

<Preparation of Coating Liquid Composition 1 for Photosensitive ResinLayer (A1)>

A three-neck flask equipped with a stirring paddle and a condenser tubewas charged with: (a) 50 parts by weight of water-soluble polyamideresin 1; (b) 34 parts by weight of water; and (c) 22 parts by weight ofethanol. The mixture was heated with stirring at 90° C. for 2 hours todissolve the water-soluble polyamide resin 1. After the solution wascooled to 70° C., (d) 1.5 parts by weight of glycidy memethacrylate(“Blemmer” G, produced by NOF Corporation) was added to the solution,followed by stirring for 30 minutes. Further added were (e) 8 parts byweight of glycerol dimethacrylate (“Blemmer” GMR, produced by NOFCorporation), (f) 24 parts by weight of 2-acroyloxyethyl-2-hydroxyethylphthalate (HOA-MPE, produced by Kyoeisha Chemical Co., Ltd.), (g) 5parts by weight of polyethylene glycol (PEG #400, produced by LionCorporation), (h) 5 parts by weight ofN,N,N′,N′-tetra(2-hydroxy-3-methacroyloxypropyl)-m-xylenediamine, (i) 4parts by weight of tetramethylolmethane triacrylate (“NK Ester” A-TMM-3,produced by Shinnakamura Chemical Industrial Co., Ltd.), (j) 1.3 partsby weight of benzyldimethyl ketal (“Irgacure” 651, produced byCiba-Geigy), and (k) 0.01 part by weight of hydroquinone monomethylether. The mixture was stirred for 30 minutes to yield coating liquidcomposition 1 for a photosensitive resin layer (A1).

<Preparation of Coating Liquid Composition 2 for Adhesion-AdjustingLayer (B1)>

Water-soluble polyamide resin 1 synthesized above was dissolved in amixed solvent of water/ethanol=50/50 (weight ratio) at 80° C. so thatthe solid content would be 15 percent by weight. Thus, coating liquidcomposition 2 for an adhesion-adjusting layer (B1) was obtained.

<Preparation of Coating Liquid Composition 3 for Heat-Sensitive MaskLayer (C1)>

A mixture of 25 parts by weight of “MA100” (carbon black, produced byMitsubishi Chemical Corporation), 26 parts by weight of nitrocotton“SL-1” (nitrocellulose, produced by Asahi Chemical Industry Co., Ltd.),6 parts by weight of plasticizer ATBC (tributyl acetylcitrate, producedby J-PLUS Co., Ltd.), and 30 parts by weight of “PM acetate” (propyleneglycol monomethyl ether acetate, produced by Osaka Printing Ink MFG.Co., Ltd.) was prepared in advance, and then kneaded and dispersed witha three-roll mill to prepare a carbon black dispersion liquid. To thedispersion liquid were added 17 parts by weight of “Araldite” 6071(epoxy resin, produced by Asahi-Ciba Limited), 24 parts by weight of“U-VAN” 2061 (melamine resin, produced by Mitsui Chemicals, Inc.), (g) 1part by weight of “Light Ester” P-1M (phosphate monomer, produced byKyoeisha Chemical Co., Ltd.), and (h) 600 parts by weight ofmethylisobutyl ketone, and the mixture was stirred for 30 minutes. Then,(d) “PM acetate” was added to the mixture so that the solid contentwould be 16 percent by weight. Thus, coating liquid composition 3 for aheat-sensitive mask layer (C1) was obtained.

<Preparation of Coating Liquid Composition 4 for Peel Assist Layer (D1)>

In a mixed solvent of water/ethanol=40/60 (weight ratio) was dissolved100 parts by weight of polyvinyl alcohol having a degree ofsaponification of 91% to 94% (“GOHSENOL” AL-06, produced by NipponSynthetic Chemical Industry Co., Ltd.) at 80° C. so that the solidcontent would be 10 percent by weight. Thus, coating liquid composition4 for a peel assist layer (D1) was obtained.

<Preparation of Coating Liquid Composition 5 for Peel Assist Layer (D2)>

In a mixed solvent of water/ethanol=40/60 (weight ratio) were dissolved100 parts by weight of polyvinyl alcohol having a degree ofsaponification of 91% to 94% (“GOHSENOL” AL-06, produced by NipponSynthetic Chemical Industry Co., Ltd.) and 2 parts by weight of ainfrared absorber (“PROJET” 825, produced by Avecia KK) at 80° C. sothat the solid content would be 10 percent by weight. Thus, coatingliquid composition 5 for a separation aid layer (D2) was obtained.

<Production of Photosensitive Resin Sheet 1>

Coating liquid composition 1 for the photosensitive resin layer (A1) wasspread on a substrate of 250 μm thick polyester film “Lumirror” S10(produced by Toray Industries Inc.) to which a polyester-based adhesivehad been applied in advance, and was dried at 60° C. for 2 hours toyield photosensitive resin sheet 1 with a total thickness of 950 μm,including the thickness of the substrate. The thickness ofphotosensitive resin sheet 1 was obtained by disposing a spacer having apredetermined thickness on the substrate and by scraping out coatingliquid composition 1 of the portion extending out of the spacer with alevel metal straight edge.

<Production of Heat-Sensitive Mask Element 1>

A 100 μm thick polyester film “Lumirror” S10 (produced by TorayIndustries Inc.) was used as the layer (E). Coating liquid composition 4was applied onto the polyester film with a bar coater so that thethickness would be 0.5 μm after drying, and dried at 120° C. for 30seconds to yield a composite of peel assist layer (D1)/protective layer(E).

Then, coating liquid composition 3 was applied onto the peel assistlayer (D1) of the resulting composite with a bar coater so that thethickness would be 2 μm after drying, and dried at 140° C. for 20seconds to yield heat-sensitive mask element 1, which is a composite ofheat-sensitive mask layer (C1)/peel assist layer (D1)/protective layer(E). The optical density (orthochromatic filter, transmission mode) ofheat-sensitive mask element 1 was 3.3.

<Production of Heat-Sensitive Mask Element 2>

Coating liquid composition 5 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries Inc.) with a barcoater so that the thickness would be 0.5 μm after drying, and dried at120° C. for 30 seconds to yield a composite of peel assist layer(D2)/protective layer (E).

Then, coating liquid composition 3 was applied onto the peel assistlayer (D2) of the resulting composite with a bar coater so that thethickness would be 2 μm after drying, and dried at 140° C. for 20seconds to yield heat-sensitive mask element 2, which is a composite ofheat-sensitive mask layer (C1)/peel assist layer (D2)/protective layer(E). The optical density (orthochromatic filter, transmission mode) ofheat-sensitive mask element 2 was 3.5.

<Production of Heat-Sensitive Mask Element 3>

Coating liquid composition 5 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries) with a bar coater sothat the thickness would be 1 μm after drying, and dried at 120° C. for30 seconds to yield a composite of peel assist layer (D2)/protectivelayer (E).

Then, coating liquid composition 3 was applied onto the peel assistlayer (D2) of the resulting composite with a bar coater so that thethickness would be 2 μm after drying, and dried at 140° C. for 20seconds to yield a composite of heat-sensitive mask layer (C1)/peelassist layer (D2)/protective layer (E).

Further, coating liquid composition 2 was applied onto the heatsensitive layer (C1) with a bar coater so that the thickness would be 1μm after drying, and dried at 120° C. for 30 seconds to yieldheat-sensitive mask element 3, which is a composite ofadhesion-adjusting layer (B1)/heat-sensitive mask layer (C1)/peel assistlayer (D2)/protective layer (E). The optical density (orthochromaticfilter, transmission mode) of heat-sensitive mask element 3 was 3.5.

Example 1

A mixed solvent of water/ethanol=70/30 percent by weight was appliedonto the photosensitive resin layer (A1) of the above-describedphotosensitive resin sheet 1 with a bar coater #20 to swell thephotosensitive resin layer (A1). Then, the photosensitive resin layer(A1) was pressed together with heat-sensitive mask element 1 with aroller such that the heat-sensitive mask layer (C1) of heat-sensitivemask element 1 came into contact with the photosensitive resin layer(A1), and allowed to stand for 1 week. Thus, photosensitive resinprinting plate precursor 1 was completed which had the layered structureof substrate/photosensitive resin layer (A1)/heat-sensitive mask layer(C1)/peel assist layer (D1)/protective layer (E) deposited in thatorder.

After peel of the protective layer (E), the photosensitive resinprinting plate precursor 1 was attached on an external drum type platesetter “CDI SPARK” (manufactured by Esko-Graphics NV), equipped with afiber laser emitting light in the infrared region such that thesubstrate came into contact with the drum. A test pattern of aresolution of 156 lines per inch (including solid pattern regions, 1% to99% half tone, 1 to 8 point fine lines, and 1 to 8 point reverse patternregions) was drawn, so that the heat-sensitive mask layer (C1) wasformed into an image mask (C1′). The heat-sensitive mask layer (C1) inthe solid pattern was substantially ablated with laser light under theconditions of a laser power of 6 W and a drum rotational speed of 300rpm, without negative effects of excessive laser power, such as laserexcavation of the surface of the underlying photosensitive resin layer(A1) and deformation of the drawn pattern. In addition, theheat-sensitive mask layer (C1) was resistant to external flaws becauseof its crosslinked structure. This made it easy to handle the printingplate precursor in attaching on the plate setter. For evaluation of thescratch resistance of the heat-sensitive mask layer (C1), theunsheltered surface of printing plate precursor 1 from which theprotective layer (E) had been peeled was rubbed with a white cottoncloth wetted with water to which a load of 500 g (the weight of thefrictionizer: 200 g; additional weight: 300 g) was applied, with a colorfastness rubbing tester (tester II specified in JIS L 0823, manufacturedby Daiei Kagaku Seiki MFG. Co, Ltd.). Even after 10 reciprocations ofrubbing the surface, there was no scratch penetrating through the blackheat-sensitive mask layer (C1).

Then, the entire surface of the plate through the image mask (C1′) wasexposed to light (exposure: 900 mJ/cm²) from a super-high-pressuremercury lamp (manufactured by ORC MFG. Co., Ltd.) having a light sourcein the ultraviolet region. Subsequently, development was performed intap water of 25° C. for 1.5 minutes with a brush-type developing machineFTW430II (manufactured by Toray Industries Inc.) equipped with a PBT(polybutylene terephthalate) brush. Consequently, the peel assist layer(D1), the image mask (C1′), and the portion not exposed to ultravioletlight of the photosensitive resin layer (A1), which was covered with theimage mask, were selectively developed to form a relief being thefaithful negative of the image mask (C1′). Although the heat-sensitivemask layer (C1) itself was crosslinked and hydrophobic and was thereforeinsoluble in water, the layer (C1) was able to be developed finally byrubbing with an rigid brush because the thickness was set as small as 2μm.

The resulting relief was composed of only the photosensitive resin layer(A1), containing no black image mask (C1′), and had a sharp shape. Thisis because the heat-sensitive mask layer (C1) is crosslinked andinsoluble in water. The heat-sensitive mask layer (C1) and thehydrophilic photosensitive resin layer (A1) are maintained independentlywithout mixing with each other.

Example 2

Photosensitive resin printing plate precursor 2 having the layeredstructure of substrate/photosensitive resin layer (A1)/heat-sensitivemask layer (C1)/peel assist layer (D2)/protective layer (E) deposited inthat order was produced in the same manner as in Example 1 except thatthe heat-sensitive mask element used in Example 1 was replaced withheat-sensitive mask element 2. Drawing was performed at a power of 6 Wand a drum rotational speed of 500 rpm in the same manner as inExample 1. As a result, the heat-sensitive mask layer (C1) in the regionof solid pattern was substantially ablated with laser light, withoutnegative effects of excessive laser power, such as laser excavation ofthe surface of the underlying photosensitive resin layer (A1) anddeformation of the drawn pattern. Since the peel assist layer (D2)overlying the heat-sensitive mask layer (C1) contained an infraredabsorber, the peel assist layer (D2) became easy to ablate with laserlight. Accordingly, it becomes possible to draw a pattern image at ahigher drum rotational speed than that in Example 1 (that is, at a lowerlaser power per spot). Also, exposure with a super-high-pressure lampand development with a brush-type developing machine were performed inthe same manner as in Example 1, and thus a sharp relief was formed.

Example 3

A mixed solvent of water/ethanol=70/30 percent by weight was appliedonto the photosensitive resin layer (A1) of the above-describedphotosensitive resin sheet 1 with a bar coater #20 to swell thephotosensitive resin layer (A1). Then, the photosensitive resin (A1) waspressed together with heat-sensitive mask element 3 with a roller suchthat the adhesion-adjusting layer (B1) of heat-sensitive mask element 3came into contact with the photosensitive resin layer (A1), and allowedto stand for 1 week. Thus, photosensitive resin printing plate precursor3 was completed which had the layered structure ofsubstrate/photosensitive resin layer (A1)/adhesion-adjusting layer(B1)/heat-sensitive mask layer (C1)/peel assist layer (D2)/protectivelayer (E) deposited in that order. Drawing at a power of 6 W and a drumrotational speed of 500 rpm was able to be performed for the resultingprinting plate precursor as same as in Example 2.

Exposure with a super-high-pressure lamp and development with abrush-type developing machine were performed in the same manner as inExample 1. Since the adhesion-adjusting layer (B1) was formed of thewater-soluble polyamide resin used in the photosensitive resin layer(A1), the adhesion-adjusting layer (B1) was united with thephotosensitive resin layer (A1). The hydrophilic adhesion-adjustinglayer (B1) and the water-insoluble heat-sensitive mask layer (C1) werenot mixed with each other, and thus the relief had a sharp shape.

<Preparation of Coating Liquid Composition 6 for Adhesion-AdjustingLayer (B2)>

(a) 2 Parts by weight of partially saponified polyvinyl alcohol(“Mowiol” 4-80, produced by Hoechst) was dissolved in (b) 40 parts byweight of water to yield coating liquid composition 6 for anadhesion-adjusting layer (B2).

<Preparation of Coating Liquid Composition 7 for Heat-Sensitive MaskLayer (C2)>

(a) 2 Parts by weight of carbon black (“Printex” U, produced byDegussa), (b) 8 parts by weight of partially saponified polyvinylalcohol (KP205, produced by Kuraray Co., Ltd.), (c) 20 parts by weightof n-propanol, and (d) 80 parts by weight of water were mixed andtreated in a disperser “Ultra Turrax” for 2 hours to yield coatingliquid composition 7 for a heat-sensitive mask layer (C2).

<Production of Heat-Sensitive Mask Element 4>

A 100 μm thick polyester film, “Lumirror” S10 (produced by TorayIndustries Inc.) was used as the layer (E). Coating liquid composition 7was applied onto the polyester film with a bar coater so that thethickness would be 6 μm after drying, and dried at 120° C. for 30seconds to yield a composite of heat-sensitive mask layer(C2)/protective layer (E).

Coating liquid composition 6 was applied onto the heat-sensitive masklayer (C2) of the resulting composite with a bar coater so that thethickness would be 5 μm after drying, and dried at 120° C. for 20seconds to yield heat-sensitive mask element 4, which is a composite ofadhesion-adjusting layer (B2)/heat-sensitive mask layer (C2)/protectivelayer (E). The optical density (orthochromatic filter, transmissionmode) of heat-sensitive mask element 4 was 3.4.

Comparative Example 1

A mixed solvent of water/ethanol=70/30 percent by weight was appliedonto the photosensitive resin layer (A1) of the above-describedphotosensitive resin sheet 1 with a bar coater #20 to swell thephotosensitive resin layer (A1). Then, the photosensitive resin (A1) waspressed together with heat-sensitive mask element 4 with a roller sothat the adhesion-adjusting layer (B2) of heat-sensitive mask composite4 came into contact with the photosensitive resin (A1), and allowed tostand for 1 week. Thus, photosensitive resin printing plate precursor 4was completed which had the layered structure ofsubstrate/photosensitive resin layer (A1)/adhesion-adjusting layer(B2)/heat-sensitive mask layer (C2)/protective layer (E) deposited inthat order. Drawing with a plate setter, exposure with asuper-high-pressure lamp and development with a brush-type developingmachine were performed in the same manner as in Example 1. Since theheat-sensitive mask layer (C2) was formed of carbon black dispersed in awater-soluble partially saponified polyvinyl alcohol, the heat-sensitivemask layer was weak in film strength and liable to be scratched whilethe printing plate was handled. The scratch resistance of theheat-sensitive mask layer (C2) was evaluated in the same manner as inExample 1. As a result, only one reciprocation of rubbing produced apenetrating scratch. Once a scratch occurs in the heat-sensitive masklayer (C2), the scratched portion cannot block ultraviolet light, sothat the portion where curing should be prevented will be cured. Thus,an undesired relief was formed, and which was not suitable for theprinting plate. Since the heat-sensitive mask layer (C2) is developed inwater, a water-soluble resin is used as a binder. Consequently, it wasfound that the adhesion-adjusting layer (B2) and the photosensitiveresin layer (A1), which were also soluble in water, were contaminatedwith the constituent of the heat-sensitive mask layer (C2). Thecontamination of the photosensitive resin layer (A1) with theconstituent of the heat-sensitive mask layer (C2) easily caused failurein curing the contaminated portions, thus resulting in an unsatisfactoryrelief.

<Synthesis of Water-Soluble Polyamide Resin 2>

A mixture of 10 parts by weight of ε-caprolactam, 90 parts by weight ofa nylon salt of N-(2-aminoethyl)piperazine and adipic acid, and 100parts by weight of water was placed in a stainless-steel autoclave.After the autoclave was purged with nitrogen gas, the mixture was heatedat 180° C. for 1 hour, and then water was removed from the mixture toyield water-soluble polyamide resin 2.

<Synthesis of Modified Polyvinyl Alcohol 1>

A flask equipped with a condenser tube was charged with 50 parts byweight of partially saponified polyvinyl alcohol “GOHSENOL” KL-05(degree of saponification: 78.5% to 82.0%, produced by Nippon SyntheticChemical Industry Co., Ltd.), 2 parts by weight of succinic anhydride,and 10 parts by weight of acetone, and heated at 60° C. for 6 hours.Subsequently, the condenser tube was removed to vaporize the acetone.Then, purification was performed twice by eluting unreacted succinicanhydride with 100 parts by weight of acetone. The product was driedunder reduced pressure at 60° C. for 5 hours to yield modified polyvinylalcohol 1 which has an ester bond of succinic acid and a hydroxy group.

<Preparation of Coating Liquid Composition 8 for Photosensitive ResinLayer (A2)>

A three-neck flask equipped with a stirring paddle and a condenser tubewas charged with: 7.5 parts by weight of water-soluble polyamide resin2, 47.5 parts by weight of modified polyvinyl alcohol 1, 11 parts byweight of diethylene glycol, 38 parts by weight of water, and 44 partsby weight of ethanol. The mixture was heated with stirring at 110° C.for 30 minutes and subsequently 70° C. for 90 minutes to dissolve thepolymer. Then, 3 parts by weight of “Blemmer” G (glycidyl methacrylate,produced by NOF Corporation) was added and the mixture was stirred at70° C. for 30 minutes. Further added were 12 parts by weight of“Blemmer” GMR (methacrylic acid adduct of glycidyl methacrylate,produced by NOF Corporation), 5 parts by weight of “Light Ester” G201P(acrylic acid adduct of glycidyl methacrylate, produced by KyoeishaChemical Co., Ltd.), 6 parts by weight of “Epoxy Ester” 70PA (acrylicacid adduct of propylene glycol diglycidyl ether, produced by KyoeishaChemical Co., Ltd.), 5 parts by weight of “NK Ester” A-200 (diacrylateester of polyethylene glycol having an average molecular weight of 200,produced by Shinnakamura Chemical Industrial Co., Ltd.), 0.1 part byweight of “Irgacure” 651 (benzyldimethyl ketal, produced by Ciba-Geigy),1.5 parts by weight of “Irgacure” 184 (α-hydroxy ketone, produced byCiba-Geigy), 0.01 part by weight of “Suminol Fast Cyanine Green G conc.”(acid dye, Color index C. I.: Acid Green 25, produced by SumitomoChemical Co., Ltd.), 0.01 part by weight of “Direct Sky Blue 6B”(produced by Hamamoto Senryou KK), 0.05 part by weight of “FOAMASTER”(antifoaming agent, produced by San Nopco Limited), 0.015 part by weightof “TINUVIN” 327 (UV-absorber, produced by Ciba-Geigy), 0.2 part byweight of “TTP-44”(bis-(2-{2-ethoxyethoxycarbonyl)ethylthio}octylthiophosphine, producedby Yodo Kagaku Co., Ltd.), and 0.005 part by weight of “Q-1300”(ammonium N-nitrosophenylhydroxylamine, produced by Wako Pure ChemicalIndustries, Ltd.). The mixture was stirred for 30 minutes to yieldmobile coating liquid composition 8 for a photosensitive resin layer(A2).

<Preparation of Adhesive-Coated Substrate 2>

A mixture of 260 parts by weight of “Vylon” 31SS (toluene solution ofunsaturated polyester resin, produced by Toyobo Co., Ltd.) and 2 partsby weight of “PS-8A” (benzoin ethyl ether, produced by Wako PureChemical Industries, Ltd.) was heated at 70° C. for 2 hours and, then,cooled to 30° C. To the mixture was added 7 parts by weight of ethyleneglycol diglycidyl ether dimethacrylate, followed by blending for 2hours. Further, 25 parts by weight of “Coronate” 3015E (ethyl acetatesolution of polyvalent isocyanate resin, produced by Nippon PolyurethaneIndustry Co., Ltd.) and 14 parts by weight of “EC-1368” (industrialadhesive, produced by 3M) were added to yield adhesive composition 1.

In a mixed solvent of 200 parts by weight of “SOLMIX” H-11 (alcoholmixture, Japan Alcohol Trading Co., Ltd.) and 200 parts by weight ofwater was dissolved 50 parts by weight of “GOHSENOL” KH-17 (polyvinylalcohol having a degree of saponification of 78.5% to 81.5%, produced byNippon Synthetic Chemical Industry Co., Ltd.) at 70° C. for 2 hours.Then, 1.5 parts by weight of “Blemmer” G (glycidyl methacrylate,produced by NOF Corporation) was added to the solution and blended for 1hour. Further, to the mixture were added 3 parts by weight of(dimethylamino ethyl methacrylate)/(2-hydroxyethylmethacrylate)/(methacrylic acid) copolymer (produced by KyoeishaChemical Co., Ltd.), 5 parts by weight of “Irgacure” 651 (benzyldimethylketal, produced by Ciba-Geigy), 21 parts by weight of “Epoxy Ester” 70PA(acrylic acid adduct of propylene glycol diglycidyl ether, produced byKyoeisha Chemical Co., Ltd.), and 20 parts by weight of ethylene glycoldiglycidyl ether dimethacrylate. These materials were blended for 90minutes and cooled to 50° C. Subsequently, 0.1 part by weight of“FLUORAD” TM FC-430 (produced by 3M) was added to the mixture andblended for 30 minutes to yield adhesive composition 2.

Adhesive (layer) composition 1 was applied onto 250 μm thick “Lumirror”T60 (polyester film, produced by Toray Industries) with a bar coater sothat the thickness after drying would be 40 μm, and the solvent wasremoved in an oven of 180° C. for 3 minutes. Then, adhesive (layer)composition 2 was applied onto the resulting layer with a bar coater sothat the thickness after drying would be 30 μm, followed by drying at160° C. for 3 minutes to yield adhesive-coated substrate 2.

<Production of Photosensitive Resin Sheet 2>

Adhesive-coated substrate 2 was exposed to light of asuper-high-pressure lamp at 1000 mJ/cm² from the adhesive-coated side.Then, coating liquid composition 8 for the photosensitive resin layer(A2) was spread on the adhesive-coated surface of adhesive-coatedsubstrate 2, and was dried at 60° C. for 5 hours in an oven to yieldphotosensitive resin sheet 2 having a total thickness of about 900 μm,including the thickness of the substrate. The thickness of thephotosensitive resin sheet 2 was controlled by disposing a spacer havinga predetermined thickness on the substrate and by scraping out coatingliquid composition 8 of the portion extending out of the spacer with alevel metal straightedge.

<Preparation of Coating Liquid Composition 9 for Peel Assist Layer (D3)>

4 parts by weight of “GOHSENOL” AL-06 (polyvinyl alcohol having a degreeof saponification of 91% to 94%, produced by NOF Corporation) wasdissolved in 55 parts by weight of water, 14 parts by weight ofmethanol, 10 parts by weight of n-propanol, and 10 parts by weight ofn-butanol to yield coating liquid composition 9 for a peel assist layer(D3).

<Preparation of Coating Liquid Composition 10 for Heat-Sensitive MaskLayer (C3)>

A mixture of 23 parts by weight of “MA100” (carbon black, produced byMitsubishi Chemical Corporation), 15 parts by weight of “DIANAL” BR-95(alcohol-insoluble acrylic resin, produced by Mitsubishi Rayon Co.,Ltd.), 6 parts by weight of a plasticizer ATBC (tributyl acetylcitrate,produced by J-PLUS Co., Ltd.), and 30 parts by weight of “PM acetate”(propylene glycol monomethyl ether acetate, produced by Osaka PrintingInk MFG. Co., Ltd.) was prepared in advance, and then kneaded anddispersed with a three-roll mill to prepare carbon black dispersionliquid 2. To dispersion liquid 2 were added 20 parts by weight of“Araldite” 6071 (epoxy resin, produced by Asahi-Ciba Limited), 27 partsby weight of “U-VAN” 2061 (melamine resin, produced by Mitsui Chemicals,Inc.), 0.7 parts by weight of “Light Ester” P-1M (phosphate monomer,produced by Kyoeisha Chemical Co., Ltd.), and 140 parts by weight ofmethylisobutyl ketone, and the mixture was stirred for 30 minutes. Then,“PM acetate” was added to the mixture so that the solid content would be33 percent by weight. Thus, coating liquid composition 10 for aheat-sensitive mask layer (C3) was obtained.

<Preparation of Coating Liquid Composition 11 for Heat-Sensitive MaskLayer (C4)>

A mixture of 23 parts by weight of “MA100” (carbon black, produced byMitsubishi Chemical Corporation), 15 parts by weight of “DIANAL” BR-95(alcohol-insoluble acrylic resin, produced by Mitsubishi Rayon Co.,Ltd.), 6 parts by weight of a plasticizer ATBC (tributyl acetylcitrate,produced by J-PLUS Co., Ltd.), and 30 parts by weight of diethyleneglycol monoethyl ether monoacetate was prepared in advance, and thenkneaded and dispersed with a three-roll mill to prepare carbon blackdispersion liquid 3. To dispersion liquid 3 were added 20 parts byweight of “Araldite” 6071 (epoxy resin, produced by Asahi-Ciba Limited),27 parts by weight of “U-VAN” 2061 (melamine resin, produced by MitsuiChemicals, Inc.), 0.7 part by weight of “Light Ester” P-1M (phosphatemonomer, produced by Kyoeisha Chemical Co., Ltd.), and 140 parts byweight of methylisobutyl ketone, and the mixture was stirred for 30minutes. Then, diethylene glycol monoethyl ether monoacetate was addedto the mixture so that the solid content would be 33 percent by weight.Thus, coating liquid composition 11 for a heat-sensitive mask layer (C3)was obtained.

<Preparation of Coating Liquid Composition 12 for Adhesion-AdjustingLayer (B3)>

In 41 parts by weight of methyl ethyl ketone and 41 parts by weight ofethyl Cellosolve was dissolved 18 parts by weight of “Epikote” 1256(epoxy resin, produced by Japan Epoxy Resins Co., Ltd.) to yield coatingliquid composition 12 for an adhesion-adjusting layer (B3).

<Production of Heat-Sensitive Mask Element 5>

Coating liquid composition 9 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries Inc.) with a barcoater so that the thickness would be 0.25 μm after drying, and dried at100° C. for 25 seconds to yield a composite of peel assist layer(D3)/protective layer (E). Coating liquid composition 10 was appliedonto the peel assist layer (D3) of the resulting composite with a barcoater so that the thickness would be 2 μm after drying, and dried at140° C. for 90 seconds to yield heat-sensitive mask element 5, which isa composite of heat-sensitive mask layer (C3)/peel assist layer(D3)/protective layer (E). The optical density (orthochromatic filter,transmission mode) of heat-sensitive mask element 5 was 3.8.

<Production of Heat-Sensitive Mask Element 6>

Coating liquid composition 9 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries Inc.) with a barcoater so that the thickness would be 0.25 μm after drying, and dried at100° C. for 25 seconds to yield a composite of peel assist layer(D3)/protective layer (E). Coating liquid composition 11 was appliedonto the peel assist layer (D3) of the resulting composite with a barcoater so that the thickness would be 2 μm after drying, and dried at140° C. for 90 seconds to yield heat-sensitive mask element 6, which isa composite of heat-sensitive mask layer (C4)/peel assist layer(D3)/protective layer (E). The optical density (orthochromatic filter,transmission mode) of heat-sensitive mask element 6 was 3.8.

<Production of Heat-Sensitive Mask Element 7>

Coating liquid composition 9 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries Inc.) with a barcoater so that the thickness would be 0.25 μm after drying, and dried at100° C. for 25 seconds to yield a composite of peel assist layer(D3)/protective layer (E). Coating liquid composition 10 was appliedonto the peel assist layer (D3) of the resulting composite with a barcoater so that the thickness would be 2 μm after drying, and dried at140° C. for 90 seconds to yield a composite of heat-sensitive mask layer(C3)/peel assist layer (D3)/protective layer (E). Coating liquidcomposition 12 was applied onto the peel assist layer (C3) of theresulting composite with a bar coater so that the thickness would be 1μm after drying, and dried at 140° C. for 60 seconds to yield aheat-sensitive mask element 7, which is a composite ofadhesion-adjusting layer (B3)/heat-sensitive mask layer (C3)/peel assistlayer (D3)/protective layer (E). The optical density (orthochromaticfilter, transmission mode) of heat-sensitive mask element 7 was 3.8.

Example 4

Coating liquid composition 8 was applied onto the photosensitive resinlayer (A2) of photosensitive resin sheet 2, and heat-sensitive maskelement 5 was disposed on the photosensitive resin layer (A2) to whichcoating liquid composition 8 had been applied, such that theheat-sensitive mask layer (C3) of heat-sensitive mask element 5 cameinto contact with the photosensitive resin layer (A2). These layers werelaminated with a calender roll heated to 80° C. to yield photosensitiveresin printing plate precursor 5 which had the layered structure ofadhesive-coated substrate 2/photosensitive resin layer(A2)/heat-sensitive mask layer (C3)/peel assist layer (D3)/protectivelayer (E) deposited in that order. The clearance of the calender rollwas adjusted so that the thickness of the composite would be 950 μmafter peel of the protective layer (E) from printing plate precursor 5.The applied coating liquid composition 8 was allowed to stand for aboutone week after lamination, and thereby the remaining solvent wasair-dried to form an additional thickness of the photosensitive resinlayer (A2).

After peel of the protective layer (E), the photosensitive resinprinting plate precursor 5 was attached on an external drum type platesetter “CDI SPARK” (manufactured by Esko-Graphics NV), equipped with afiber laser emitting light in the infrared region such that thesubstrate came into contact with the drum. A test pattern of aresolution of 156 lines per inch (including solid -pattern regions, 1%to 99% half tone, 1 to 8 point fine lines, and a 1 to 8 point reversepattern regions) was drawn, so that the heat-sensitive mask layer (C3)was formed into an image mask (C3′). The heat-sensitive mask layer (C3)in the solid pattern was substantially ablated with laser light underthe conditions of a laser power of 9 W and a drum rotational speed of500 rpm, without negative effects of excessive laser power, such aslaser excavation of the surface of the underlying photosensitive resinlayer (A2) and deformation of the drawn pattern.

In addition, the heat-sensitive mask layer (C3) was resistant toexternal flaws because of its crosslinked structure. This made it easyto handle of the printing plate precursor in attaching on the platesetter. The scratch resistance of the heat-sensitive mask layer (C3) wasevaluated in the same manner as in Example 1. As a result, even after 10reciprocations of rubbing the surface, there was no scratch penetratingthrough the black heat-sensitive mask layer (C3).

Then, the entire surface of the plate through the image mask (C3′) wasexposed to light (exposure: 1000 mJ/cm²) from a super-high-pressuremercury lamp manufactured by ORC MFG. Co., Ltd.) having a light sourcein the ultraviolet region.

Subsequently, development was performed in tap water of 35° C. for 1.5minutes with a brush-type developing machine FTW500II (manufactured byToray Industries Inc.) equipped with a PBT (polybutylene terephthalate)brush. Consequently, the peel assist layer (D3), the image mask (C3′),and the portion not exposed to ultraviolet light of the photosensitiveresin layer (A2), which was covered with the image mask, wereselectively developed to form a relief being the faithful negative ofthe image mask (C3′). Although the heat-sensitive mask layer (C3) itselfwas crosslinked and hydrophobic, and was therefore insoluble in water,the layer (C3) was able to be developed finally by setting the thicknessof the layer (C3) as small as 2 μm and by mechanically rubbing with anrigid brush.

The resulting relief was composed of only the photosensitive resin layer(A2), containing no black image mask (C3′), and had a sharp shape. Thisis because the heat-sensitive mask layer (C3) is crosslinked andinsoluble in water. The heat-sensitive mask layer (C3) and thehydrophilic photosensitive resin layer (A2) are maintained independentlywithout mixing with each other.

Example 5

Coating liquid composition 8 was applied onto the photosensitive resinlayer (A2) of photosensitive resin sheet 2, and heat-sensitive maskelement 6 was disposed on the photosensitive resin layer (A2) to whichcoating liquid composition 8 had been applied, such that theheat-sensitive mask layer (C4) of heat-sensitive mask element 6 cameinto contact with the photosensitive resin layer (A2). These layers werelaminated with a calender roll heated to 80° C. to yield photosensitiveresin printing plate precursor 6 which has the layered structure ofadhesive-coated substrate 2/photosensitive resin layer(A2)/heat-sensitive mask layer (C4)/peel assist layer (D3)/protectivelayer (E) deposited in that order. The clearance of the calender rollwas adjusted so that the thickness of the composite would be 950 μmafter peel of the protective layer (E) from printing plate precursor 6.The applied coating liquid composition 8 was allowed to stand for aboutone week after lamination, and thereby the remaining solvent wasair-dried to form an additional thickness of the photosensitive resinlayer (A2).

After peel of the protective layer (E), the photosensitive resinprinting plate precursor 6 was attached on an external drum type platesetter “CDI SPARK” (manufactured by Esko-Graphics NV), equipped with afiber laser emitting light in the infrared region such that thesubstrate came into contact with the drum. A test pattern of aresolution of 156 lines per inch (including solid pattern regions, 1% to99% halftone, 1 to 8 point fine lines, and a 1 to 8 point reversepattern regions) was drawn, so that the heat-sensitive mask layer (C4)was formed into an image mask (C4′). The heat-sensitive mask layer (C4)in the solid pattern was substantially ablated with laser light underthe conditions of a laser power of 9 W and a drum rotational speed of500 rpm, without negative effects of excessive laser power, such aslaser excavation of the surface of the underlying photosensitive resinlayer (A2) and deformation of the drawn pattern. In addition, theheat-sensitive mask layer (C4) was resistant to external flaws becauseof its crosslinked structure. This made it easy to handle the printingplate precursor in attaching on the plate setter. The scratch resistanceof the heat-sensitive mask layer (C4) was evaluated in the same manneras in Example 1. As a result, even after 10 reciprocations of rubbingthe surface, there was no scratch penetrating through the blackheat-sensitive mask layer (C4).

Then, the entire surface of the plate through the image mask (C4′) wasexposed to light (exposure: 1000 mJ/cm²) from a super-high-pressuremercury lamp (manufactured by ORC MFG. Co., Ltd.) having a light sourcein the ultraviolet region.

Subsequently, development was performed in tap water of 35° C. for 1.5minutes with a brush-type developing machine FTW500 II (manufactured byToray Industries Inc.) equipped with a PBT (polybutylene terephthalate)brush. Consequently, the peel assist layer (D3), the image mask (C4′),and the portion not exposed to ultraviolet light of the photosensitiveresin layer (A2), which was covered with the image mask, wereselectively developed to form a relief being the faithful negative ofthe image mask (C4′). Although the heat-sensitive mask layer (C4) itselfwas crosslinked and hydrophobic, and was therefore insoluble in water,the layer (C4) was able to be developed finally by setting the thicknessof the layer (C4) as small as 2 μm and by mechanically rubbing with anrigid brush.

The resulting relief was composed of only the photosensitive resin layer(A2), containing no black image mask (C4′), and had a sharp shape. Thisis because the heat-sensitive mask layer (C4) is crosslinked andinsoluble in water. The heat-sensitive mask layer (C4) and thehydrophilic photosensitive resin layer (A2) are maintained independentlywithout mixing with each other.

Example 6

Coating liquid composition 8 was applied onto the photosensitive resinlayer (A2) of photosensitive resin sheet 2, and heat-sensitive maskelement 7 was disposed on the photosensitive resin layer (A2) to whichcoating liquid composition 8 had been applied, such that theadhesion-adjusting layer (B3) of the heat-sensitive mask element 7 cameinto contact with the photosensitive resin layer (A2). These layers werelaminated with a calender roll heated to 80° C. to yield photosensitiveresin printing plate precursor 7 which had the layered structure ofadhesive-coated substrate 2/photosensitive resin layer(A2)/adhesion-adjusting layer (B3)/heat-sensitive mask layer (C3)/peelassist layer (D3)/protective layer (E) deposited in that order. Theclearance of the calender roll was adjusted so that the thickness of thecomposite would be 950 μm after peel of the protective layer (E) fromthe printing plate precursor 7. The applied coating liquid composition 8was allowed to stand for about one week after lamination, and therebythe remaining solvent was air-dried to form an additional thickness ofthe photosensitive resin layer (A2).

After peel of the protective layer (E), photosensitive resin printingplate precursor 7 was attached on an external drum type plate setter“CDI SPARK” (manufactured by Esko-Graphics NV), equipped with a fiberlaser emitting light in the infrared region such that the substrate cameinto contact with the drum. A test pattern of a resolution of 156 linesper inch (including solid pattern regions, 1% to 99% half tone, 1 to 8point fine lines, and a 1 to 8 point reverse pattern regions) was drawn,so that the heat-sensitive mask layer (C3) was formed into an image mask(C3′). The heat-sensitive mask layer (C3) in the solid pattern wassubstantially ablated with laser light under the conditions of a laserpower of 9 W and a drum rotational speed of 500 rpm, without negativeeffects of excessive laser power, such as laser excavation of thesurface of the underlying photosensitive resin layer (A2) anddeformation of the drawn pattern. In addition, the heat-sensitive masklayer (C3) was resistant to external flaws because of its crosslinkedstructure. This made it easy to handle the printing plate precursor inattaching on the plate setter.

Then, the entire surface of the plate through the image mask (C3′) wasexposed to light (exposure: 1000 mJ/cm²) from a super-high-pressuremercury lamp (manufactured by ORC MFG. Co., Ltd.) having a light sourcein the ultraviolet region.

Subsequently, development was performed in tap water of 35° C. for 1.5minutes with a brush-type developing machine FTW500II (manufactured byToray Industries Inc.) equipped with a PBT (polybutylene terephthalate)brush. Consequently, the peel assist layer (D3), the image mask (C3′),and the portion not exposed to ultraviolet light of the photosensitiveresin layer (A2), which was covered with the image mask, wereselectively developed to form a relief being the faithful negative ofthe image mask (C3′). Although the heat-sensitive mask layer (C3) itselfwas crosslinked and hydrophobic, and was therefore insoluble in water,the layer (C3) was able to be developed finally by setting the thicknessof the layer (C3) as small as 2 μm and by mechanically rubbing with anrigid brush.

The resulting relief was composed of only the photosensitive resin layer(A2), containing no black image mask (C3′), and had a sharp shape. Thisis because the heat-sensitive mask layer (C3) is crosslinked andinsoluble in water. The heat-sensitive mask layer (C3) and thehydrophilic photosensitive resin layer (A2) are maintained independentlywithout mixing with each other.

<Production of Heat-Sensitive Mask Element 8>

Coating liquid composition 9 was applied onto a 100 μm thick polyesterfilm “Lumirror” S10 (produced by Toray Industries Inc.) with a barcoater so that the thickness would be 0.25 μm after drying, and dried at100° C. for 25 seconds to yield a composite of peel assist layer(D3)/protective layer (E). An aluminum thin film was formed on the peelassist layer (D3) of the resulting composite by vacuum vapor depositionto yield heat-sensitive mask element 8, which is a composite ofheat-sensitive mask layer (C5)/peel assist layer (D3)/protective layer(E) and which has an optical density (orthochromatic filter,transmission mode) of 3.5.

<Production of Heat-Sensitive Mask Element 9>

Heat-sensitive mask element 9 was produced in the same manner as inheat-sensitive mask element 8, except that the layer (C5) ofheat-sensitive mask element 8 was replaced with a layer (C6) formed bymetal vapor deposition of tellurium. The optical density (orthochromaticfilter, transmission mode) of element 9 was 3.8.

Example 7

Coating liquid composition 8 was applied onto the photosensitive resinlayer (A2) of photosensitive resin sheet 2, and the heat-sensitive maskelement 8 was disposed on the photosensitive resin layer (A2) to whichcoating liquid composition 8 had been applied, such that theheat-sensitive mask layer (C5) of heat-sensitive mask element 8 cameinto contact with the photosensitive resin layer (A2). These layers werelaminated with a calender roll heated to 80° C. to yield photosensitiveresin printing plate precursor 8 which has the layered structure ofadhesive-coated substrate 2/photosensitive resin layer(A2)/heat-sensitive mask layer (C5)/peel assist layer (D3)/protectivelayer (E) deposited in that order. The clearance of the calender rollwas adjusted so that the thickness of the composite would be 950 μmafter peel of the protective layer (E) from the printing plate precursor8. The applied coating liquid composition 8 was allowed to stand forabout one week after lamination, and thereby the remaining solvent wasair-dried to form an additional thickness of the photosensitive resinlayer (A2).

The heat-sensitive mask layer (C5) can be subjected to laser drawingunder the conditions of a laser power of 9 W and drum rotational speedof 500 rpm, as in Example 4, without negative effects, such as laserexcavation of the surface of the underlying photosensitive resin layer(A2) and deformation of the drawn pattern.

The scratch resistance of the heat-sensitive mask layer (C5) wasevaluated in the same manner as in Example 1. Although a penetratingscratch occurred by 7 reciprocations of rubbing the surface, theheat-sensitive mask layer can be used in practice.

Exposure of the entire surface with a super-high-pressure mercury lampand development with water were performed in the same manner as inExample 4 to yield a letterpress printing plate having a sharp relief.Since the heat-sensitive mask layer (C5) is made of metal thin film ofaluminium and is not mixed with the photosensitive resin layer (A2), thephotosensitive resin layer (A2) can be cured with light without negativeeffects. Although aluminum metal itself is insoluble in water, theheat-sensitive mask layer (C5) can be scrubbed out with an rigid brushbecause the thickness is very small, thus, finally developed with water.

Example 8

Photosensitive resin printing plate precursor 9 was produced in the samemanner as in Example 7, except that heat-sensitive mask element 8 wasreplaced with heat-sensitive mask element 9.

The laser drawing on the heat-sensitive mask layer (C6) can be performedunder conditions of a substantially lower energy density than in Example7 using the aluminum deposition film, that is, a laser power of 6 W anddrum rotational speed of 500 rpm, without laser excavation of thesurface of the underlying photosensitive resin layer (A2) anddeformation of the drawn pattern.

As for the scratch resistance of the heat-sensitive mask layer (C6), apenetrating scratch occurred by 7 reciprocations of rubbing the surface,but there was no problem in practice. Mass transfer is not observedbetween the heat-sensitive mask layer (C6) and the photosensitive resinlayer (A2), and hence the photosensitive resin layer (A2) can be curedwith light without negative effects. Although tellurium metal isinsoluble in water, the heat-sensitive mask layer (C6) can be scrubbedout with an rigid brush because the thickness is very small, thus,finally developed with water.

<Production of Heat-Sensitive Mask Element 10>

Heat-sensitive mask element 10, which is a composite of heat-sensitivemask layer (C2)/peel assist layer (D1)/protective layer (E) was producedin the same process as in Example 1, except that coating liquid 3 forthe layer (C1) of heat-sensitive mask composite 1 used in Example 1 wasreplaced with coating liquid 7 for the layer (C2), the dried thicknessof the layer (C2) was set at 6 μm, and the layer (C2) was dried at 120°C. for 30 seconds. The optical density (orthochromatic filter,transmission mode) of the resulting heat-sensitive mask element 10 was3.4.

<Production of Heat-Sensitive Mask Element 11>

Heat-sensitive mask element 11, which is a composite of heat-sensitivemask layer (C2)/peel assist layer (D3)/protective layer (E), wasproduced in the same process as in Example 4, except that coating liquid10 for the layer (C3) of heat-sensitive mask element 5 used in Example 4was replaced with coating liquid 7 for the layer (C2), the driedthickness of the layer (C2) was set at 6 μm, and the layer (C2) wasdried at 120° C. for 30 seconds. The optical density (orthochromaticfilter, transmission mode) of the resulting heat-sensitive mask element11 was 3.4.

Comparative Example 2

Photosensitive resin printing plate precursor 10, which is a compositeof substrate/photosensitive resin layer (A1)/heat-sensitive mask layer(C2)/peel assist layer (D1)/protective layer (E), was produced in thesame process as in Example 1, except that heat-sensitive mask element 1was replaced with heat-sensitive mask element 10. The resulting printingplate precursor was different from printing plate precursor 1 evaluatedin Example 1 in that non-crosslinked, water-soluble heat-sensitive masklayer (C2) was used instead of heat-sensitive mask layer (C1) having acrosslinked structure.

The precursor was evaluated as in Example 1. As a result, problemsresulting from the use of non-crosslinked, water-soluble heat-sensitivemask layer (C2) occurred as in Comparative Example 1, such as lowscratch resistance of the heat-sensitive mask layer and deterioration ofthe relief reproduction due to mass transfer between the layer (C) andthe layer (A).

Comparative Example 3

Photosensitive resin printing plate precursor 11, which is a compositeof substrate/photosensitive resin layer (A2)/heat-sensitive mask layer(C2)/peel assist layer (D3)/protective layer (E), was produced in thesame process as in Example 4, except that heat-sensitive mask element 5was replaced with heat-sensitive mask element 11. The resulting printingplate precursor was different from the printing plate precursor 5evaluated in Example 4 in that non-crosslinked, water-solubleheat-sensitive mask layer (C2) was used instead of heat-sensitive masklayer (C3) having a crosslinked structure.

The precursor was evaluated as in Example 4. As a result, problemsresulting from the use of non-crosslinked, water-soluble heat-sensitivemask layer (C2) occurred as in Comparative Example 1, such as lowscratch resistance of the heat-sensitive mask layer and deterioration ofthe relief reproduction due to mass transfer between layer (C) and layer(A).

TABLE 1 Structure of photosensitive resin printing plate precursorExample Comparative example component description 1 2 3 4 5 6 7 8 1 2 3Support Substrate 1 coated with polyester adhesive Adhesive-coatedsubstrate 2 Same as Example 1 Same as Example 4 Photosensitive resinIdentifier Layer (A1) Layer (A2) Layer (A1) Layer (A2) layer (A)Water/alcohol-soluble or Water-soluble polyamide resin 1: Water-solublepolyamide resin 2: 7.5 parts by weight Same as Example 1 Same asdispersible resin 50 parts by weight Modified polyvinyl alcohol 1: 47.5parts by weight Example 4 UV-curable monomer Blemmer G: 1.5 parts byweight Blemmer G: 3 parts by weight Blemmer GMR: 8 parts by weightBlemmer GMR: 12 parts by weight HOA-MPE: 24 parts by weight Light EsterG201P: 5 parts by weight N,N-tetra(2-hydroxy-3- Epoxy Ester 70PA: 6parts by weight methacroyloxypropyl)-m- NK Ester A-200: 5 parts byweight xylenediamine: 5 parts by weight NK Ester A-TMM-3: 4 parts byweight Adhesion-adjusting Identifier Not provided Not provided Layer(B1) Not provided Not provided Layer (B3) Not provided Not providedLayer (B2) Not provided Not provided layer (B) Water/alcohol-soluble orWater-soluble (not “Mowiol” 4–80 dispersible resin polyamide resin 1contained) Water-insoluble resin (not contained) “Epikote”1256 (notcontained) Heat-sensitive mask Identifier Layer (C1) Layer(C3) Layer(C4) Layer (C3) Layer (C5) Layer (C6) Layer (C2) layer (C) IR-absorbablematerial “MA 100” (carbon black): 25 parts by weight “MA 100” (carbonblack): 23 parts Vapor- Vapor- “Printex” U (carbon black): 2 parts byUV-absorbable material by weight deposited deposited weight Pyrolyzablecompound Nitrocotton “SL-1”(nitrocellulose): “DIANAL” BR-95 (acrylicresin): 15 aluminum tellurium (Not contained) 26 parts by weight partsby weight film film Water insolubilizer “Araldite” 6071: 17 parts byweight “Araldite” 6071: 20 parts by weight (Not contained) “U-VAN” 2061:24 parts by weight “U-VAN” 2061: 27 parts by weightWater/alcohol-soluble or (Nitrocotton SL-1 is dissolved in alcohol.)(Not contained) “KP205”: 8 parts by weight dispersible resin Solvent*¹for coating Solvent A Solvent A Solvent B Solvent A (Not used)n-Propanol liquid Solvent C Solvent C Solvent C Solvent C Water Peelassist layer (D) Identifier Layer (D1) Layer (D2) Layer (D3) (Notprovided) Layer (D1) Layer (D3) Resin GOHSENOL GOHSENOL AL-06: 100 partsGOHSENOL AL-06: Same as Same as AL-06 by weight Example 1 Example 4IR-absorbable material (Not PRPJET 825: 2 parts by weight (Notcontained) contained) Protective layer (E) Lumirror S10 (thickness: 100μm) Production of Photosensitive resin sheet Sheet 1 Sheet 2 Sheet 1Sheet 2 photosensitive resin Heat-sensitive mask Element 1 Element 2Element 3 Element 5 Element 6 Element 7 Element 8 Element 9 Element 4Element 10 Element 11 printing plate element precursor Photosensitiveresin Precursor 1 Precursor 2 Precursor 3 Precursor 5 Precursor 6Precursor 7 Precursor 8 Precursor 9 Precursor 4 Precursor 10 Precursor11 printing plate precursor *¹Solvent A: “PM acetate” (propylene glycolmonomethyl ether acetate) Solvent B: diethylene glycol monoethyl ethermonoacetate Solvent C: methylisobutyl ketone

TABLE 2 Example Comparative Example 1 2 3 4 5 6 7 8 1 2 3 Step (1)Printing plate 1 to 1 to 3, 7, 1 to 3, 1 to 3, 7 to 10 1 to 3, 5, 1, 4,7, 8, 10 None structure 3, 7, 10, 11 5 to 7 to 10 Corresponding 10 10,11 claims Step (2) Conditions for Drawing with CDI SPARK (fiber laser)drawing 6 W 6 W 9 W 6 W 6 W 9 W mask pattern 300 500 rpm 500 rpm 500 rpm300 rpm 500 rpm on layer (C) rpm with IR laser Step (3) Formation of UVexposure with super-high-pressure mercury lamp latent image 900 mJ/cm²1000 mJ/cm² 900 mJ/cm² 1000 with UV light mJ/cm² Step (4) Development25° C. tap water 35° C. tap water 25° C. tap water 1.5 min 1.5 min 1.5min Scratch resistance Layer (C1) Layer (C3) Layer (C4) Layer (C3) Layer(C5) 7 Layer (C6) 7 Layer (C2) 1 of heat-sensitive mask >10 >10 >10 >10layer (C) (number of scrubs to form penetrating scratch) Layer (C)/Layer(A) None Occurred mass transfer Resulting relief Sharp Deformed

1. A photosensitive resin printing plate precursor for letterpressprinting comprising, on a support in this order: a photosensitive resinlayer (A) containing a water-soluble or water-dispersible resin and anultraviolet-curable monomer; optionally, an adhesion-adjusting layer (B)containing a water-soluble or water-dispersible resin; a water-insolubleheat-sensitive mask layer (C) containing an infrared-absorbing material,a peel assist layer (D) having a thickness of 0.1 to 6 μm, and aprotective layer (E), wherein the absence of the adhesion-adjustinglayer (B), the water insoluble heat-sensitive mask layer (C) is formedin contact with the photosensitive resin layer (A), and in the presenceof the adhesion-adjusting layer (B), the water-insoluble heat-sensitivemask layer (C) is formed in contact with the adhesion adjusting layer(B).
 2. The photosensitive resin printing plate precursor according toclaim 1, wherein the water-insoluble heat-sensitive mask layer (C)contains crosslinked curable resin.
 3. The photosensitive resin printingplate precursor according to claim 2, wherein the curable resin is acombination of: at least one compound selected from the group consistingof multifunctional isocyanates and multifunctional epoxy compounds; andat least one compound selected from the group consisting of urea-basedresins, amine-based compounds, amide-based compounds, hydroxylgroup-containing compounds, carboxylic compounds, and thiol-basedcompounds.
 4. The photosensitive resin printing plate precursoraccording to claim 1, wherein the water-insoluble heat-sensitive masklayer (C) is a metal thin film.
 5. The photosensitive resin printingplate precursor according to claim 1, further comprising anadhesion-adjusting layer (B) between the photosensitive resin layer (A)and the heat-sensitive mask layer (C).
 6. The photosensitive resinprinting plate precursor according to claim 5, wherein theadhesion-adjusting layer (B) contains a water-soluble or awater-dispersible resin.
 7. The photosensitive resin printing plateprecursor according to claim 1, wherein the photosensitive resin layer(A) contains a polyamide resin.
 8. The photosensitive resin printingplate precursor according to claim 1, wherein the photosensitive resinlayer (A) contains polyvinyl alcohol, partially saponified polyvinylalcohol, or their modified form.
 9. The photosensitive resin printingplate precursor according to claim 1, wherein the heat-sensitive masklayer (C) contains an acrylic resin and no nitrocellulose.
 10. Thephotosensitive resin printing plate precursor according to claim 1,wherein the peel assist layer (D) contains an infrared-absorbingmaterial and/or a pyrolyzable compound.
 11. The photosensitive resinprinting plate precursor according to claim 1, wherein the peel assistlayer (D) remains on the heat-sensitive mask layer side after peelingoff the protective layer (E).
 12. The photosensitive resin printingplate precursor according to claim 1, wherein the photosensitive resinlayer (A) contains a water-soluble or water-dispersible resin andultraviolet-curable monomer, without elastmeric binder.
 13. A method forproducing a photosensitive resin printing plate precursor, the methodcomprising the steps of: (i) forming a photosensitive resin sheet bydepositing a photosensitive resin layer (A) on a substrate; (ii) forminga heat-sensitive mask element including a water-insoluble heat-sensitivemask layer (C), a protective layer (E) and a peel assist layer (D)having a thickness of 0.1 to 6 μm disposed between the protective layer(E) and the heat-sensitive mask layer (C); and (iii) laminating thesurface of the photosensitive resin layer (A) of the photosensitiveresin sheet to the heat-sensitive mask layer (C) of the heat-sensitivemask element.
 14. The method for producing the photosensitive resinprinting plate precursor according to claim 13, wherein theheat-sensitive mask element includes the heat-sensitive mask layer (C)and an adhesion-adjusting layer (B), and the lamination is performedsuch that the adhesion-adjusting layer (B) of the heat-sensitive maskelement comes into contact with the surface of the photosensitive resinlayer (A).
 15. The method for producing the photosensitive resinprinting plate precursor according to claim 13, wherein, in the step offorming the heat-sensitive mask element, the heat-sensitive mask layer(C) is deposited while being heated, thereby forming a crosslinkedstructure therein.
 16. A method for producing a letterpress printingplate comprising: (1) preparing a photosensitive resin printing plateprecursor comprising, on a support in this order: a photosensitive resinlayer (A) containing a water-soluble or water-dispersible resin and anultraviolet-curable monomer; a water-insoluble heat-sensitive mask layer(C) containing an infrared-absorbing material; a peel assist layer (D)having a thickness of 0.1 to 6 μm and a protective layer (E); (2)forming an image mask (C′) by imagewise irradiating the heat-sensitivemask layer (C) with infrared laser light; (3) exposing through the imagemask (C′) to ultraviolet light to form a latent image on thephotosensitive resin layer (A); and (4) removing the image mask (C′) andportions unexposed to ultraviolet light of the photosensitive resinlayer (A) by development with a water-based liquid, wherein at leastpart of the protective layer (E) is peeled before the heat-sensitivemask layer (C) is imagewise irradiated with infrared laser light.